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Afnetworking crash course

2022-07-28 14:26:00 【51CTO】

AFNetworking Crash course

 

The Internet — Your program cannot survive without it ！ Apple Foundation framework Medium NSURLConnection And very difficult to understand , However, there is an alternative that can be used ：​ ​AFNetworking​​.

AFNetworking Very popular with developers – It has won the favor of our readers ：2012 The best iOS Library prize （​ ​2012 Best iOS Library Award​​.） So now I will write this article to introduce you how to use it effectively in the program .

AFNetworking It includes all the content you need to interact with online resources , from web services To file download . When your program is downloading a large file ,AFNetworking It can also ensure your UI Is responsive .

 

This article will introduce AFNetworking The main components of the framework . Along the way , You will use ​ ​World Weather Online​​ Advice provided (Feeds) To create a weather (Weather) Program . The weather data used at the beginning is static , But after learning the content of this article , The program will be connected to real-time weather consultation .

Expected today ： A cool developer learns all about AFNetworking knowledge , And use in his program AFNetworking. Let's get busy ！

Start

First come here （​ ​here​​） Download the startup project for this article . This project provides a basic UI — AFNetworking The relevant code has not been added .

open MainStoryboard.storyboard file , Will see 3 individual view controller：


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From left to right , Namely ：

  • top (top-level) Navigation controller for ;
  • Used to display the weather table view controller, One line a day ;
  • A custom view controller (WeatherAnimationViewController) When a user clicks on a table view cell when , This view controller The weather consultation of a certain day will be displayed .

Build and run the project , You will see relevant UI appear , But nothing has been achieved ！ Because the program needs to get the required data from the network , The relevant code has not been added . This is what you will achieve in this article ！

First , You need to AFNetworking The framework is included in the project . If you haven't AFNetworking Words , Download the latest version here ：​ ​GitHub​​.

When you unzip the downloaded file , You will see one of them AFNetworking A folder , Full of .h and .m file , Highlighted below :


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take AFNetworking Drag and drop to Xcode In Engineering .


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When the option to add a file appears , Make sure that... Is checked Copy items into destination group’s folder (if needed)  and  Create groups for any added folders.

To complete the relevant configuration , Please work in Supporting Files Open the precompiled header file in the Group Weather-Prefix.pch. And then in other import Add the following line of code after ：

           
           

            
            #import "AFNetworking.h"
           
           

           
           
    
            
            
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take AFNetworking Add to precompiled header file , This means that the framework will be automatically added to all source code files of the project .

be prone to , isn't it? ？ Now you're ready “ The weather ” Program code ！

operation JSON

AFNetworking It is very intelligent to load and process structured data through the network , ordinary HTTP The same is true of requests . In particular, it supports JSON, XML and Property Lists (plists).

You can download some JSON data , Then use your own parser to parse , But why this ？ adopt AFNetworking You can complete these operations ！

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First , You need to test the script （ data ） A basic requirement URL. Put the following static NSString Declare to WTTableViewController.m Top , That's all #import below ：

           
           

            
            static NSString *const BaseURLString [email protected]"http://www.raywenderlich.com/downloads/weather_sample/";
           
           

           
           
    
            
            
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This URL It's a very simple one “web service”, In this article, I specially created for you . If you want to know what it looks like , You can download the code here ：​ ​download the source​​.

This web service With 3 Different formats （JSON, XML and PLIST） Return weather data . You can use the following URL Take a look at the returned data ：

The first data format uses ​ ​JSON​​. JSON It is a common JavaScript Derived class object format . It looks like :

           
           

            
            { "data": { "current_condition": [ { "cloudcover": "16", "humidity": "59", "observation_time": "09:09 PM", } ] } }
           
           

           
           
    
            
            
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Be careful :  If you want to tie more about JSON Content , Please refer to ：​ ​Working with JSON in iOS 5 Tutorial​​.

When the user clicks JSON Button , What you want from the service JSON Data is loaded and processed . stay WTTableViewController.m in , find jsonTapped:  Method ( It should be empty now ) , And replace with the following code ：

           
           

            
            - (IBAction)jsonTapped:(id)sender { // 1 NSString *weatherUrl = [NSStringstringWithFormat:@"%@weather.php?format=json", BaseURLString]; NSURL *url = [NSURLURLWithString:weatherUrl]; NSURLRequest *request = [NSURLRequest requestWithURL:url];   // 2AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request // 3 success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {self.weather  = (NSDictionary *)JSON; self.title = @"JSON Retrieved"; [self.tableView reloadData]; } // 4 failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError*error, id JSON) { UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather" message:[NSString stringWithFormat:@"%@",error] delegate:nil cancelButtonTitle:@"OK"otherButtonTitles:nil]; [av show]; }];   // 5 [operation start]; }
           
           

           
           
    
            
            
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This is your first AFNetworking Code ！ therefore , It looks brand new , I will introduce the code in this method .

  1. According to the basic URL Construct a complete URL. Then through this complete URL To obtain a NSURL object , And then according to this url To obtain a NSURLRequest.
  2. AFJSONRequestOperation Is a fully functional class （all-in-one）— It integrates the acquisition of data from the network and JSON To analyze .
  3. When the request is successful , Then run the successful block （success block）. In this example , Analyze the weather data from JSON The variable is converted to a dictionary （dictionary）, And store it in the attribute weather in .
  4. If something goes wrong , Then run the failed block （failure block）, For example, the network is unavailable . If failure block Is called the , The error message will be displayed through the prompt box .

As shown above ,AFNetworking Is very simple to use . If you want to use what Apple provides APIs（ Such as NSURLConnection） To do the same thing （ Download and parse JSON data ）, It takes a lot of code to do .

Now the weather data already exists in self.weather in , You need to show it . find tableView:numberOfRowsInSection:  Method , And replace with the following code ：

           
           

            
            - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in the section.   if(!self.weather) return 0;   switch (section) {case 0:{ return 1; } case 1:{ NSArray *upcomingWeather = [self.weather upcomingWeather]; return[upcomingWeather count]; } default: return 0; } }
           
           

           
           
    
            
            
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table view There are two section： The first one is used to display the current weather , The second one is used to show the future weather .

Wait a minute , You may be thinking . there  [self.weather upcomingWeather] What is it? ?  If self.weather It's a common NSDictionary, How does it know “upcomingWeather” What is it? ?

In order to analyze the data more easily , stay starter In Engineering , There is a pair of NSDictionary categories：

  • NSDictionary+weather.m
  • NSDictionary+weather_package.m

these categories Added some convenient methods , Through these methods, you can easily access the data elements in the dictionary . So you can focus on the network , instead of NSDictionary Data access in . Right ？

go back to  WTTableViewController.m, find  tableView:cellForRowAtIndexPath:  Method , And replace with the following implementation ：

           
           

            
            - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath*)indexPath { static NSString *CellIdentifier = @"WeatherCell"; UITableViewCell *cell =[tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];NSDictionary *daysWeather;   switch (indexPath.section) { case 0:{ daysWeather = [self.weather currentCondition]; break; } case 1:{ NSArray *upcomingWeather = [self.weather upcomingWeather]; daysWeather = [upcomingWeather objectAtIndex:indexPath.row]; } default: break; }  cell.textLabel.text = [daysWeather weatherDescription];   // maybe some code will be added here later...   return cell; }
           
           

           
           
    
            
            
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Follow tableView:numberOfRowsInSection: The method is the same , Convenient... Is used here NSDictionary categories To get the data . The weather of the current day is a dictionary , The weather of the next few days is stored in an array .

Generate and run the project , And then click JSON Button . This will dynamically get a AFJSONOperation object , And see the following picture ：


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JSON Successful operation !

operation Property Lists(plists)

Property lists ( Or for short plists) In a certain format （ Apple defines ） Composed of XML file . Apples will generally plists Used in user settings . It looks like ：

      
      

       
       data current_condition cloudcover 16 humidity 59
      
      

      
      
    
       
       
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It means ：

  • A dictionary has a name “data” Of key, This key Corresponding to another dictionary .
  • This dictionary has a name “current_condition” Of key, This key Corresponding to a array.
  • This array contains a dictionary , There are many in the dictionary key and values. such as cloudcover=16 and humidity=59.

Now it's time to load plist Version of the weather data ！ find plistTapped:  Method , And replace with the following implementation ：

           
           

            
            -(IBAction)plistTapped:(id)sender{ NSString *weatherUrl = [NSStringstringWithFormat:@"%@weather.php?format=plist",BaseURLString]; NSURL *url = [NSURLURLWithString:weatherUrl]; NSURLRequest *request = [NSURLRequest requestWithURL:url];  AFPropertyListRequestOperation *operation = [AFPropertyListRequestOperation propertyListRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id propertyList) { self.weather  = (NSDictionary *)propertyList; self.title = @"PLIST Retrieved"; [self.tableView reloadData]; } failure:^(NSURLRequest*request, NSHTTPURLResponse *response, NSError *error, id propertyList) { UIAlertView *av =[[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather" message:[NSStringstringWithFormat:@"%@",error] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [av show]; }];   [operation start]; }
           
           

           
           
    
            
            
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be aware , The above code is almost the same as JSON Consistency of version , It's just going to operate （operation） Type from AFJSONOperation It is amended as follows AFPropertyListOperation. This is very neat ： You just need to modify a little bit of code to receive JSON or plist Data in format ！

Generate and run the project , And then click PLIST Button . You will see the following ：


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If you need to reset everything , To restart the operation , At the top of the navigation bar Clear The button can be cleared title and table view Data in .

operation XML

AFNetworking Handle JSON and plist The parsing of uses a similar method , It doesn't take much effort , And deal with XML It's a little more complicated . below , According to XML Consult to build a weather dictionary （NSDictionary）.

iOS Provides a help class ：NSXMLParse ( If you want to know more , Please see the link here ：​ ​SAX parser​​).

Still in the file WTTableViewController.m, find  xmlTapped:  Method , And replace with the following implementation ：

           
           

            
            - (IBAction)xmlTapped:(id)sender{ NSString *weatherUrl = [NSStringstringWithFormat:@"%@weather.php?format=xml",BaseURLString]; NSURL *url = [NSURLURLWithString:weatherUrl]; NSURLRequest *request = [NSURLRequest requestWithURL:url];  AFXMLRequestOperation *operation = [AFXMLRequestOperation XMLParserRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, NSXMLParser*XMLParser) { //self.xmlWeather = [NSMutableDictionary dictionary]; XMLParser.delegate = self;[XMLParser setShouldProcessNamespaces:YES]; [XMLParser parse]; } failure:^(NSURLRequest*request, NSHTTPURLResponse *response, NSError *error, NSXMLParser *XMLParser) { UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather" message:[NSStringstringWithFormat:@"%@",error] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [av show]; }];   [operation start]; }
           
           

           
           
    
            
            
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Up to now , This seems to be the same as the previous treatment JSON and plist Is very similar . The biggest change is in the success block （success block） in , It will not pass you a preprocessed NSDictionary object . It is AFXMLRequestOperation Instantiated NSXMLParse object , This object will be used to handle heavy XML Parsing tasks .

NSXMLParse Object has a group delegate Method is what you need to achieve — Used to obtain XML data . Be careful , In the above code, I will XMLParser Of delegate Set to self, therefore WTTableViewController Will be used to deal with XML The parsing task of .

First , Update WTTableViewController.h  And modify the class declaration , As shown below ：

           
           

            
            @interface WTTableViewController : UITableViewController<NSXMLParserDelegate>
           
           

           
           
    
            
            
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The above code means that this class will implement （ follow ）NSXMLParserDelegate agreement . The next step will be the following delegate Method declarations are added to @implementation Back :

           
           

            
            - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary*)attributeDict; - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string; -(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString*)namespaceURI qualifiedName:(NSString *)qName; -(void) parserDidEndDocument:(NSXMLParser*)parser;
           
           

           
           
    
            
            
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In order to support the analysis of information , You also need some attributes to store relevant data . Add the following code to @implementatio Back :

           
           

            
            @property(strong) NSMutableDictionary *xmlWeather; //package containing the complete [email protected](strong) NSMutableDictionary *currentDictionary; //current section being [email protected](strong) NSString *previousElementName; @property(strong) NSString *elementName;@property(strong) NSMutableString *outstring;
           
           

           
           
    
            
            
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Then open WTTableViewController.m, Now you need to implement the above mentioned ones one by one delegate Method . Paste the following method into the implementation file ：

           
           

            
            - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary*)attributeDict  { self.previousElementName = self.elementName;   if (qName) { self.elementName = qName; }   if([qName isEqualToString:@"current_condition"]){ self.currentDictionary =[NSMutableDictionary dictionary]; } else if([qName isEqualToString:@"weather"]){self.currentDictionary = [NSMutableDictionary dictionary]; } else if([qName isEqualToString:@"request"]){ self.currentDictionary = [NSMutableDictionary dictionary]; }  self.outstring = [NSMutableString string]; }
           
           

           
           
    
            
            
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When NSXMLParser When a new element start tag is found , Will call the above method . In this method , Construct a new dictionary to store the assigned value to currentDictionary Properties before , First save the last element name . Try to make outstring Reset , This string is used to construct XML The data in the tag .

Then paste the following method behind the previous method ：

           
           

            
            - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if(!self.elementName){ return; }   [self.outstring appendFormat:@"%@", string]; }
           
           

           
           
    
            
            
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Like the name , When NSXMLParser In a XML Character data found in tag , Will call this method . This method appends character data to outstring Properties of the , When XML At the end of the tag , This outstring Will be dealt with .

continue , Paste the following method behind the previous method ：

           
           

            
            - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {   // 1 if([qName isEqualToString:@"current_condition"] || [qName isEqualToString:@"request"]){ [self.xmlWeather setObject:[NSArray arrayWithObject:self.currentDictionary] forKey:qName]; self.currentDictionary = nil; } // 2 else if([qName isEqualToString:@"weather"]){   // Initalise the list of weather items if it dosnt exist NSMutableArray *array = [self.xmlWeather objectForKey:@"weather"]; if(!array) array = [NSMutableArray array];   [array addObject:self.currentDictionary]; [self.xmlWeather setObject:array forKey:@"weather"];  self.currentDictionary = nil; } // 3 else if([qName isEqualToString:@"value"]){ //Ignore value tags they only appear in the two conditions below } // 4 else if([qName isEqualToString:@"weatherDesc"] || [qName isEqualToString:@"weatherIconUrl"]){[self.currentDictionary setObject:[NSArray arrayWithObject:[NSDictionarydictionaryWithObject:self.outstring forKey:@"value"]] forKey:qName]; } // 5 else {[self.currentDictionary setObject:self.outstring forKey:qName]; }   self.elementName = nil; }
           
           

           
           
    
            
            
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When the end tag of the element is detected , Will call the above method . In this method , Will find some tags ：

  1. urrent_condition The element represents the weather of today . Today's weather will be added directly to xmlWeather In the dictionary .
  2. weather The element represents the weather of the next day . There is only one weather today , And the following weather has many , So here , Add the subsequent weather to an array .
  3. value Tags appear in other tags , So this label can be ignored here .
  4. weatherDesc and weatherIconUrl The value of the element is stored before , Need to be put into an array — The structure here is to connect with JSON and plist The version of the weather advisory format matches .
  5. All other elements are as is （as-is） stored .

Here is the last one delegate Method ！ Paste the following method behind the previous method ：

           
           

            
            -(void) parserDidEndDocument:(NSXMLParser *)parser { self.weather = [NSDictionarydictionaryWithObject:self.xmlWeather forKey:@"data"]; self.title = @"XML Retrieved";[self.tableView reloadData]; }
           
           

           
           
    
            
            
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When NSXMLParser Resolved to document At the end of , Will call this method . Here it is ,xmlWeather The dictionary has been constructed ,table view It can be reloaded .

In the above code xmlWeather Add to a dictionary , It seems redundant , However, this can ensure that JSON and plist The format of the version exactly matches . So all of 3 Data formats （JSON, plist and XML） Can be displayed with the same code ！

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Now all of delegate Methods and properties are all done , find xmlTapped:  Method , And uncomment the successful block （success block） One line of code in ：

           
           

            
            -(IBAction)xmlTapped:(id)sender{ ... success:^(NSURLRequest *request, NSHTTPURLResponse*response, NSXMLParser *XMLParser) { // the line below used to be commented out self.xmlWeather = [NSMutableDictionary dictionary]; XMLParser.delegate = self; ... }
           
           

           
           
    
            
            
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Generate and run projects , And then click XML Button , You will see the following ：


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A small weather program

Um. , The above program doesn't seem to have a friendly experience , It's a bit like rainy days all week . How to make table view The weather information experience in is better ？

Take a closer look at the previous JSON Format data ：​ ​JSON format from before​​, You will see a picture in each weather item URLs.  Show these weather pictures to each table view cell in , In this way, the program will look more interesting .

AFNetworking to UIImageView Added a category, Make pictures load asynchronously , That is to say, when the pictures are downloaded in the background , programmatic UI The interface is still responsive . To use this function , First, you need to put this category import To WTTableViewController.m Top of file ：

      
      

       
       #import "UIImageView+AFNetworking.h"
      
      

      
      
    
       
       
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        find tableView:cellForRowAtIndexPath:  Method , And paste the following code into the last return cell;  Code above （ There should be a comment mark here ）
      
      

      
      
    
       
       
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            __weak UITableViewCell *weakCell = cell;   [cell.imageView setImageWithURLRequest:[[NSURLRequest alloc] initWithURL:[NSURL URLWithString:daysWeather.weatherIconURL]]placeholderImage:[UIImage imageNamed:@"placeholder.png"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image){ weakCell.imageView.image = image;   //only required if no placeholder is set to force the imageview on the cell to be laid out to house the new image. //if(weakCell.imageView.frame.size.height==0 || weakCell.imageView.frame.size.width==0 ){ [weakCell setNeedsLayout]; //} }failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error){   }];
           
           

           
           
    
            
            
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First create a weak reference (weak) Of cell, So you can do it block Use this cell. If you visit directly cell Variable ,Xcode There will be a prompt about retain Warnings of loops and memory leaks .

UIImageView+AFNetworking category Defined a setImageWithURLRequest…  Method . The parameters of this method include ： A pointing image URL Request , A placeholder picture , One success block And a failure block.

When cell When it was first created ,cell Medium UIImageView A placeholder image will be displayed , Until the real image is downloaded . Here you need to make sure that the placeholder image is the same size as the actual image .

If the dimensions are different , You can success block Call in cell Of setNeedsLayout Method . Two lines of code are commented in the above code , This is because the placeholder image here is just the right size , Leave notes , It may be used in other programs .

Now generate and run the project , Then click on the previously added 3 Any of the operations , You will see the following ：


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very good ! Loading pictures asynchronously has never been easier .

One RESTful class

Up to now, you have used similar AFJSONRequestOperation Such a class creates a one-time HTTP request . in addition , Lower level AFHTTPClient Class is used to access a single web service terminal . For this AFHTTPClient It is usually set with a basic URL, And then use AFHTTPClient Make multiple requests （ Not like before , Every time I ask , all Create a AFHTTPClient）.

AFHTTPClient It is also the coding parameter 、 Handle multipart Form request body Construction 、 Managing request operations and batch queueing operations provides great flexibility , It also Handled the whole set RESTful (GET, POST, PUT, and DELETE), Now let's try the two most commonly used ：GET and POST.

Be careful :  Yes REST, GET and POST Unclear ？ Take a look at the interesting introduction here – How can I explain to my wife REST(​ ​How I Explained REST to My Wife​​.)

stay WTTableViewController.h  At the top, modify the class declaration as follows ：

           
           

            
            @interface WTTableViewController : UITableViewController
           
           

           
           
    
            
            
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stay  WTTableViewController.m in , find httpClientTapped:  Method , And replace with the following implementation ：

           
           

            
            - (IBAction)httpClientTapped:(id)sender { UIActionSheet *actionSheet = [[UIActionSheet alloc]initWithTitle:@"AFHTTPClient" delegate:self cancelButtonTitle:@"Cancel"destructiveButtonTitle:nil otherButtonTitles:@"HTTP POST",@"HTTP GET", nil]; [actionSheet showFromBarButtonItem:sender animated:YES]; }
           
           

           
           
    
            
            
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The above method will pop up a action sheet, To select GET and POST request . Paste the following code to achieve action sheet The corresponding operation of the button in ：

           
           

            
            - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex{// 1 NSURL *baseURL = [NSURL URLWithString:[NSString stringWithFormat:BaseURLString]];NSDictionary *parameters = [NSDictionary dictionaryWithObject:@"json" forKey:@"format"];   // 2AFHTTPClient *client = [[AFHTTPClient alloc] initWithBaseURL:baseURL]; [client registerHTTPOperationClass:[AFJSONRequestOperation class]]; [client setDefaultHeader:@"Accept"value:@"application/json"];   // 3 if (buttonIndex==0) { [client postPath:@"weather.php"parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {self.weather = responseObject; self.title = @"HTTP POST"; [self.tableView reloadData]; }failure:^(AFHTTPRequestOperation *operation, NSError *error) { UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather" message:[NSStringstringWithFormat:@"%@",error] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [av show];   } ]; } // 4 else if (buttonIndex==1) { [client getPath:@"weather.php"parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {self.weather = responseObject; self.title = @"HTTP GET"; [self.tableView reloadData]; }failure:^(AFHTTPRequestOperation *operation, NSError *error) { UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather" message:[NSStringstringWithFormat:@"%@",error] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [av show];   } ]; } }
           
           

           
           
    
            
            
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The above code works as follows :

  1. Construct a baseURL, And a parameter dictionary , And pass these two variables to AFHTTPClient.
  2. take AFJSONRequestOperation register as HTTP The operation of , In this way, it can be the same as the previous example , You can get parsed JSON data .
  3. Made a GET request , This request has a pair block：success and failure.
  4. POST Please follow GET equally .

ad locum , Will request a JSON Respond , Of course, you can also use the other two formats discussed before to replace JSON.

Generate and run the project , Click on HTTPClient Button , And then choose GET or POST Button to initialize a related request . Then you will see the following ：


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thus , You already know AFHTTPClient The most basic way to use . however , There is a better way to use it , It can make the code cleaner and tidier , Let's learn about it .

Connect to Live Service

Up to now , You are already in table view controller Called directly in AFRequestOperations and AFHTTPClient. actually , Most of the time it's not like this , Your network request will be with someone web service or API relevant .

AFHTTPClient Have the ability to communicate with web API All contents of the communication .AFHTTPClient The network communication part has been coupled in the code , The code of network communication can be reused in the whole project .

Here are two questions about AFHTTPClient Best practice guidance ：

  1. For each web service Create a subclass . for example , If you are writing a social network aggregator , Then maybe there will be Twitter A subclass of ,Facebook A subclass of ,Instragram And so on .
  2. stay AFHTTPClient In subclass , Create a class method , Used to return a shared singleton , This will save resources and save the necessary object creation .

At present , There is no one in your project AFHTTPClient Subclasses of , Now let's create one . Let's deal with it , Let the code clean up .

First , Create a new file in the project ：iOSCocoa TouchObjective-C Class. Name it WeatherHTTPClient  And let it inherit from AFHTTPClient.

You want this class to do 3 thing ：

A： perform HTTP request

B： When new weather data is available , call delegate

C： Use the user's current geographical location to get accurate weather .

Replace with the following code WeatherHTTPClient.h:

           
           

            
            #import "AFHTTPClient.h"   @protocol WeatherHttpClientDelegate;   @interface WeatherHTTPClient : AFHTTPClient   @property(weak) id delegate;   + (WeatherHTTPClient *)sharedWeatherHTTPClient;- (id)initWithBaseURL:(NSURL *)url; - (void)updateWeatherAtLocation:(CLLocation *)location forNumberOfDays:(int)number;   @end   @protocol WeatherHttpClientDelegate -(void)weatherHTTPClient:(WeatherHTTPClient *)client didUpdateWithWeather:(id)weather; -(void)weatherHTTPClient:(WeatherHTTPClient *)client didFailWithError:(NSError *)error; @end
           
           

           
           
    
            
            
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In the implementation file , You will learn more about the definition in the header file . open WeatherHTTPClient.m  And add the following code to @implementation below :

           
           

            
            + (WeatherHTTPClient *)sharedWeatherHTTPClient { NSString *urlStr [email protected]"http://free.worldweatheronline.com/feed/";   static dispatch_once_t pred; staticWeatherHTTPClient *_sharedWeatherHTTPClient = nil;   dispatch_once(&pred, ^{_sharedWeatherHTTPClient = [[self alloc] initWithBaseURL:[NSURL URLWithString:urlStr]]; });return _sharedWeatherHTTPClient; }   - (id)initWithBaseURL:(NSURL *)url { self = [super initWithBaseURL:url]; if (!self) { return nil; }   [self registerHTTPOperationClass:[AFJSONRequestOperation class]]; [self setDefaultHeader:@"Accept" value:@"application/json"];  return self; }
           
           

           
           
    
            
            
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sharedWeatherHTTPClient Methods use Grand Central Dispatch（GCD） To ensure that the shared singleton object is initialized and allocated only once . I'm going to use a base URL To initialize the object , And set it as expected web service The response is a JSON.

Paste the following method under the previous method ：

           
           

            
            - (void)updateWeatherAtLocation:(CLLocation *)location forNumberOfDays:(int)number{NSMutableDictionary *parameters = [NSMutableDictionary dictionary]; [parameters setObject:[NSString stringWithFormat:@"%d",number] forKey:@"num_of_days"]; [parameters setObject:[NSString stringWithFormat:@"%f,%f",location.coordinate.latitude,location.coordinate.longitude]forKey:@"q"]; [parameters setObject:@"json" forKey:@"format"]; [parameters setObject:@"7f3a3480fc162445131401" forKey:@"key"];   [self getPath:@"weather.ashx"parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {if([self.delegate respondsToSelector:@selector(weatherHTTPClient:didUpdateWithWeather:)])[self.delegate weatherHTTPClient:self didUpdateWithWeather:responseObject]; }failure:^(AFHTTPRequestOperation *operation, NSError *error) { if([self.delegate respondsToSelector:@selector(weatherHTTPClient:didFailWithError:)]) [self.delegate weatherHTTPClient:self didFailWithError:error]; }]; }
           
           

           
           
    
            
            
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This method calls World Weather Online Interface , To get the weather information of the specific location .

It's very important ！ In this example API key Just created for this article . If you create a program , Please be there. ​ ​World Weather Online​​ Create an account , And get your own API key！

Once the object obtains the weather data , It needs some way to inform the interested objects ： The data is back . Thank you here WeatherHttpClientDelegate Agreement and its delegate Method , In the code above success and failure blocks You can inform one controller： The weather at the designated location has been updated . such ,controller You can update the weather .

Now? , We need to integrate these code fragments ！WeatherHTTPClient Want to receive a location information , also WeatherHTTPClient Definition One. delegate agreement , Right now WTTableViewControlle Class to update , To use the WeatherHTTPClient.

open WTTableViewController.h  Add one import, And replace with the following code @interface Statement :

           
           

            
            #import "WeatherHTTPClient.h"   @interface WTTableViewController : UITableViewController
           
           

           
           
    
            
            
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Add a new Core Location manager attribute :

           
           

            
            @property(strong) CLLocationManager *manager;
           
           

           
           
    
            
            
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stay  WTTableViewController.m in , Add the following code to viewDidLoad: The bottom of ：

           
           

            
            self.manager = [[CLLocationManager alloc] init]; self.manager.delegate = self;
           
           

           
           
    
            
            
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The above two lines of code initialize Core Location manager, So when view When loading , Used to determine the current location of the user .Core Location And then it will pass delegate Callback to return location information . Add the following method to the implementation file ：

           
           

            
            - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{   //if the location is more than 5 minutes old ignore if([newLocation.timestamp timeIntervalSinceNow]< 300){ [self.manager stopUpdatingLocation];   WeatherHTTPClient *client = [WeatherHTTPClient sharedWeatherHTTPClient]; client.delegate = self; [client updateWeatherAtLocation:newLocation forNumberOfDays:5];  } }
           
           

           
           
    
            
            
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Now? , When the user's location changes , You can use it WeatherHTTPClient Single example to request the weather information of the current location .

remember ,WeatherHTTPClient There are two delegate Method needs to implement . Add the following two methods to the implementation file ：

           
           

            
            -(void)weatherHTTPClient:(WeatherHTTPClient *)client didUpdateWithWeather:(id)aWeather{self.weather = aWeather; self.title = @"API Updated"; [self.tableView reloadData]; }   -(void)weatherHTTPClient:(WeatherHTTPClient *)client didFailWithError:(NSError *)error{UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather" message:[NSString stringWithFormat:@"%@",error] delegate:nil cancelButtonTitle:@"OK"otherButtonTitles:nil]; [av show]; }
           
           

           
           
    
            
            
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The above two methods , When WeatherHTTPClient The request is successful , You can update the weather data and reload table view. If the network is wrong , An error message is displayed .

find apiTapped:  Method , And replace with the following method ：

           
           

            
            -(IBAction)apiTapped:(id)sender{ [self.manager startUpdatingLocation]; }
           
           

           
           
    
            
            
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Build and run programs , Click on AP Button to initialize a WeatherHTTPClient request , Then you will see the following picture :


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I hope your future weather here is the same as mine ： a sunny day ！

I'm not dead yet ！

You may have noticed , The external call here web service It takes some time to return data . When operating on the network , It is very important to provide users with an information feedback , Only in this way can users know whether the program is running or has crashed .

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Fortunately ,AFNetworking There is a simple way to provide feedback ：AFNetworkActivityIndicatorManager.

stay  WTAppDelegate.m in , find application:didFinishLaunchingWithOptions:  Method , And replace with the following method ：

           
           

            
            - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions { [AFNetworkActivityIndicatorManager sharedManager].enabled = YES; return YES;}
           
           

           
           
    
            
            
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Give Way sharedManager It can automatically display the network activity indicator （ network activity indicator）— Whenever you shoot , As long as there is a new network request running in the background . So you don't have to ask every time , Should be managed separately .

Generate and run the project , whenever , As long as there is a network request , You can see a small network fire wheel in the status bar ：


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Now? , Even if your program is waiting for a slow web service, Users know that the program is still running !

Download the pictures

If you are in the table view cell Click on , The program will switch to the detailed picture of the weather , And the corresponding weather conditions are displayed in an animated way .

This is very good , But at present, there is only one background image in animation . In addition to updating the background image through the network , Is there a better way ！

The following is the introduction of this article AFNetworking The last content of ：AFImageRequestOperation.  Follow AFJSONRequestOperation equally , AFImageRequestOperation Encapsulates the HTTP request ： Get photo .

stay WeatherAnimationViewController.m  There are two methods that need to be implemented . find updateBackgroundImage:  Method , And replace with the following code :

           
           

            
            - (IBAction)updateBackgroundImage:(id)sender {   //Store this image on the same server as the weather canned files NSURLRequest *request = [NSURLRequest requestWithURL:[NSURLURLWithString:@"http://www.scott-sherwood.com/wp-content/uploads/2013/01/scene.png"]]; AFImageRequestOperation *operation = [AFImageRequestOperation imageRequestOperationWithRequest:request imageProcessingBlock:nil success:^(NSURLRequest *request, NSHTTPURLResponse*response, UIImage *image) { self.backgroundImageView.image = image; [self saveImage:image withFilename:@"background.png"]; } failure:^(NSURLRequest *request, NSHTTPURLResponse*response, NSError *error) { NSLog(@"Error %@",error); }]; [operation start]; }
           
           

           
           
    
            
            
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This method initializes and downloads a new background image . At the end , It will return the requested complete picture .

stay WeatherAnimationViewController.m in , You will see two auxiliary methods ：imageWithFilename: and saveImage:withFilename:, Through these two auxiliary methods , You can store and load the downloaded pictures .updateBackgroundImage: The downloaded pictures will be stored on disk through auxiliary methods .

Next find deleteBackgroundImage:  Method , And replace with the following code :

           
           

            
            - (IBAction)deleteBackgroundImage:(id)sender { NSString *path; NSArray *paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); path = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"WeatherHTTPClientImages/"];   NSError *error;[[NSFileManager defaultManager] removeItemAtPath:path error:&error];   NSString *desc =[self.weatherDictionary weatherDescription]; [self start:desc]; }
           
           

           
           
    
            
            
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This method will delete the downloaded pictures , So when testing the program , You can download the pictures again .

The last time ： Generate and run the project , Download weather data , And click a cell, To open the detailed weather screen . In the detailed weather picture , Click on Update Background Button . If you click sunny cell, You will see the following picture ：


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come from :http://www.raywenderlich.com/zh-hans/36079/afnetworking

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