Review-singleton mode, review-Mode

Review-singleton mode, review-Mode

1. Singleton)

* Ensure that only one object is created for a class.

2. Role

* Saves memory overhead.

* If some data is used in the entire program, you only need to use the same resource (ensure that the data accessed by everyone is the same)

* Generally, the tool class is designed as a singleton mode.

3. Implementation

* MRC

* ARC

SoundTool. h

1 # import <Foundation/Foundation. h> 2 3 @ interface SoundTool: NSObject <NSCopying> 4 5 + (instancetype) Explain SoundTool; 6 7 @ endView Code

SoundTool. m

# Import "SoundTool. h "@ implementation SoundToolstatic id _ instance = nil; + (instancetype) allocWithZone :( struct _ NSZone *) zone {if (_ instance = nil) {static dispatch_once_t onceToken; dispatch_once (& onceToken, ^ {_ instance = [super allocWithZone: zone] ;});} return _ instance ;}+ (instancetype) export soundtool {return [[self alloc] init];}-(instancetype) init {static dispatch_once_t onceToken; dispatch_once (& onceToken, ^ {_ instance = [super init];}); return _ instance;} + (instancetype) copyWithZone :( struct _ NSZone *) zone {return _ instance;} + (instancetype) mutableCopyWithZone :( struct _ NSZone *) zone {return _ instance;} // The following three are not used by ARC-(oneway void) release {}-(instancetype) retain {return _ instance;}-(NSUInteger) retainCount {return 1 ;}View Code

4. It is recommended to package it into a macro.