單例模式-用GCD實現,模式-GCD實現

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單例模式-用GCD實現,模式-GCD實現

用GCD實現單例模式的步驟:

步驟1. 建立標頭檔 XZSingleton.h,裡面代碼如下:

// .h檔案#define XZSingletonH(name) + (instancetype)shared##name;// .m檔案#if __has_feature(objc_arc)    #define XZSingletonM(name) \    static id _instace; \ \    + (id)allocWithZone:(struct _NSZone *)zone \    { \        static dispatch_once_t onceToken; \        dispatch_once(&onceToken, ^{ \            _instace = [super allocWithZone:zone]; \        }); \        return _instace; \    } \ \    + (instancetype)shared##name \    { \        static dispatch_once_t onceToken; \        dispatch_once(&onceToken, ^{ \            _instace = [[self alloc] init]; \        }); \        return _instace; \    } \ \    - (id)copyWithZone:(NSZone *)zone \    { \        return _instace; \    }#else    #define XZSingletonM(name) \    static id _instace; \ \    + (id)allocWithZone:(struct _NSZone *)zone \    { \        static dispatch_once_t onceToken; \        dispatch_once(&onceToken, ^{ \            _instace = [super allocWithZone:zone]; \        }); \        return _instace; \    } \ \    + (instancetype)shared##name \    { \        static dispatch_once_t onceToken; \        dispatch_once(&onceToken, ^{ \            _instace = [[self alloc] init]; \        }); \        return _instace; \    } \ \    - (id)copyWithZone:(NSZone *)zone \    { \        return _instace; \    } \ \    - (oneway void)release { } \    - (id)retain { return self; } \    - (NSUInteger)retainCount { return 1;} \    - (id)autorelease { return self;}#endif

 

步驟2. 要實現的單例類,比如 XZDataTool,XZDataTool.h   XZDataTool.m代碼分別 如下:

#import <Foundation/Foundation.h>@interface XZDataTool : NSObjectXZSingletonH(DataTool)@end
#import "XZDataTool.h"@implementation XZDataToolXZSingletonM(DataTool)@end

 

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