Internal implementation principle of yymodel

YYModel As a model transformation framework in the development process , by JSON And data model , Provides a high-performance solution .

I've been listening to others before ,YYModel The internal implementation is KVC Attribute assignment . It is also considered reasonable , But today, I found the source code , In fact, it is not used setValue：forKey： The way of assignment . Instead, it adopted objc_msgSend Method called the setter Method . in the future , Tell people YYModel Don't say yes KVC 了 , At first glance, I haven't seen the source code . Next stick a sentence assignment source

case YYEncodingTypeNSMutableString: {
                    if ([value isKindOfClass:[NSString class]]) {
                        if (meta->_nsType == YYEncodingTypeNSString) {
                            ((void (*)(id, SEL, id))(void *) objc_msgSend)((id)model, meta->_setter, value);
                        } else {
                            ((void (*)(id, SEL, id))(void *) objc_msgSend)((id)model, meta->_setter, ((NSString *)value).mutableCopy);
                        }
                    } 

It's clearly written inside ((void (*)(id, SEL, id))(void *) objc_msgSend)((id)model, meta->_setter, value);

Next, I'll write down the general process of the transformation between the model and the data I see .

Json turn Model

We usually call methods yy_modelWithJson Perform the conversion operation . In fact, this function mainly implements the next four steps ：

1、 First of all json Serialize to an available dictionary , And then call yy_modelWithDictionary Method

2、yy_modelWithDictionary Yes Json Type determination , Create instances of objects through class objects , And pass yy_modelSetWithDictionary Assign a value

3、 stay yy_modelSetWithDictionary In the method , adopt modelSetValueForProperty Method assignment .

4、modelSetValueForProperty To judge the attribute data type , And then sent through the invoked message objc_msgSend The way , Call again setter Method .

 

Model turn Json

Usually we call yy_modelToJSONString Method to convert . The implementation process of this function is roughly like this ：

1、 By calling yy_modelToJSONData Back to data, And then through [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding] Generated json character string

2、yy_modelToJSONData Method call yy_modelToJSONObject Method returns a id Object of type , And then through [NSJSONSerialization dataWithJSONObject:jsonObject options:0 error:NULL] Generate what you need in the first step NSData.

3、yy_modelToJSONObject Call in ModelToJSONObjectRecursive Method .

4、 then ModelToJSONObjectRecursive It mainly preprocesses objects , To become effective json object .

ModelToJSONObjectRecursive Method process

• ModelToJSONObjectRecursive Method for direct transfer json Between the attributes of .
• For attributes of collection classes, such as dictionaries 、 Array, etc. through recursive calls ModelToJsonObjectRecursive Method to constantly check whether each element can be directly transferred json. If you can directly return the collection class , If not , Create a new collection , Traverse every element before , Turn the elements inside into NSString、NSNumber, Then add it to the collection class after parsing .
• Custom class object , Use NSDictionary Object to reassemble , adopt objc_msgSend call getter The method value of , Then turn into effective one by one json object .

️： The above is my personal conclusion by checking the source code , If there are mistakes, please correct them , Mutual encouragement