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 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
To modify the MRC project to Arc:
Xcode edit-"refactor-" Convert to OC ARC
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Let some. m files in the ARC project do not use arc
Project configuration-"Build phases-" Compile sources
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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/3321237/1745690
OBJECTIVE-C (9) Arc of memory management