Relive-Singleton mode

1. Single case design mode (Singleton)

* Ensure that the object created by a class will always have only one

2. Role

* Save memory overhead.

* If some of the data is used throughout the program, only the same resources (to ensure that the data you access are the same)

* Generally, tool design is suitable for single case mode

3. Implement

* MRC

* ARC

SoundTool.h

1 #import <Foundation/Foundation.h>23@interface Soundtool:nsobject < Nscopying>45 + (instancetype) Sharesoundtool; 6 7 @end

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soundtool.m

#import "SoundTool.h"@implementationSoundtoolStatic ID_instance =Nil;+ (Instancetype) Allocwithzone: (struct_nszone *) zone{if(_instance = =Nil) {        Staticdispatch_once_t Oncetoken; Dispatch_once (&oncetoken, ^{_instance=[Super Allocwithzone:zone];    }); }    return_instance;}+(instancetype) sharesoundtool{return[[Self alloc] init];}-(instancetype) init{Staticdispatch_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 for non-arc use-(OneWayvoid) release{}-(instancetype) retain{return_instance;}-(Nsuinteger) retaincount{return 1;}

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4. Recommended packaging for use as a macro

Relive-Singleton mode