OC-ARC (Automatic Reference Counting) automatic reference counting

ZRC Notes

1. Cannot call:
retain, release, autorelease, retainCount, @selector(retain), dealloc
The system will call these automatically

2. Replace NSAutoReleasePool with @autoreleasepool
@autoreleaasepool
{
/* Perform a series of operations * can use break,returen,goto */
}

3. You can rewrite dealloc yourself but don't release the instance object in delloc, you can release some default types such as int, char, FIFE

int *a; FIFE *p; free(a);fclose(p);

and don't call [super dealloc];

The conversion between the 4.id type and the void* type cannot be performed, but it can be achieved through the __bridge modifier

5. When compiling, the __autoreleasing modifier will be added to the double pointer variable of the function automatically, for example

-(id)initWithErrir:(NSError **)error;// will be compiled as-(id)initWithErrir:(__autoreleasing NSError **)error;

6. It is required that the initial value of the variable must be nil
7. The functions that operate memory such as memset, bzero, memcpy cannot be used. ARC will monitor the behavior of these functions.)
8. When ARC is in effect, OC objects cannot be defined in C language structure questions. The compiler cannot automatically release the OC objects inside the structure. If it must be used, use the __unsage_unretained modifier to modify the OC variables in the structure.The advantage is that the compiler will not care about the memory of this variable at all. The disadvantage is that it needs to be managed manually
If you use the terminal to compile the code, use clang together and add the compile option -fobjc-arc

Method family

Because retain and release are automatically added by the system, the system needs to know which functions are related to object production
Therefore, the collection of methods related to object production is called "method family", which mainly requires special naming rules
SatisfyReturn value, method category
The selector is the same as the method family name (starting with _ can be ignored)
The name of the selector consists of the family name plus a string starting with a non-lowercase letter
Usually init/alloc/beginning of new/copy/mutableCopy

Automatically convert to ARC

edit->Refactor find the widget Convert to Objective-C ARC
Code that uses garbage collection cannot be automatically converted to ARC-enabled code

Macros to manage ARC

The declaration of the macro should be placed at the end of the method
NS_RERTURNS_RETAINED
Indicate that this method is the same as the method at the beginning of init or copy, and the caller is responsible for releasing the returned object
That is, although this function is not an ARC naming ruleBut let him be managed by ARC
NS_RERTURNS_NOT_RETAINED
Indicates that this method is not a memory management method, and the caller does not need to release the returned object
Simply put, this function must not be managed by ARC
For example
-(void)initName NS_RERTURNS_NOT_RETAINED;
Originally, this function with init should be managed by ARC, but after adding NS_RERTURNS_NOT_RETAINED, it is no longer needed

Determine if ARC is valid

Judging by conditional compilation
#if(__has_feature(objc_arc)) is valid if true