OBJECTIVE-C (9) Arc of memory management

• ARC mechanism and judging criteria

Arc:auto Reference counting Automatic reference count

is a compiler mechanism to add retain, release, Autorelease and other methods to our code during the compilation process.

Forced to use after iOS7.0, so that programmers no longer care about memory management, requirements:

1) cannot use retain release and other methods of reference counting

2) You cannot use the Autorelease method, but you can use the auto-release pool

3) Override the Dealloc method to no longer use [super Dealloc]

Judging criteria:

Object is freed as long as no strong pointer is pointed to the object

Strong pointer:__strong (default)

Weak pointer:__weak

Do not appear with this code:

__weak person *p = [[Person alloc] init];

Method Autorelease is not allowed under the ARC mechanism, but is not discarded @autoreleasepool

ARC is simply a code call to help you join retain/release/autorelease at compile time.

Therefore, the use of @autoreleasepool under arc is still valid, ensuring that objects in the pool are delayed release.

• @property Memory Management parameters

@property Memory Management parameter strong represents a strong pointer property, weak the table weakness pointer parameter.

Simple memory: When the property is OC object

Use strong instead of retain

Use weak instead of assign. Using the weak parameter to resolve circular reference problems

Mrc:

Retain:release property old value, retain property new value

Assign: Direct assignment without changing the reference count (default)

Generally used for non-OC objects, and without the possession of objects

Copy:release old value, copy new value, commonly used for nsstring

ARC:

Strong: Strong pointer, equivalent to retain, for object

Weak: weak pointer, for object

Assign: For non-OC objects

Copy: For NSString

• MRC and Arc

To modify the MRC project to Arc:

Xcode edit-"refactor-" Convert to OC ARC

Let some. m files in the ARC project do not use arc

Project configuration-"Build phases-" Compile sources

Sets the compiler flags:-fno-objc-arc for the specified. m file

Use arc for some. m files in non-ARC projects:

Compiler Flags:-f-objc-arc

This article is from the "Teacheran" blog, make sure to keep this source http://annmeng.blog.51cto.com/3321237/1745626

OBJECTIVE-C (9) Arc of memory management