iOS开发——单例模式

　　一、用if语句实现单例

　　

1.在.h文件中

#import <Foundation/Foundation.h>

@interface YYTRequestTool : NSObject

+(id)sharedYYTRequestTool;

@end

　　2.在.m文件中

#import "YYTRequestTool.h"

@interface YYTRequestTool ()

@property(nonatomic,strong) DPAPI *api;

@end

@implementation YYTRequestTool

static YYTRequestTool *sharedYYTRequestTool = nil;

+(id)sharedYYTRequestTool{

if (!sharedYYTRequestTool) {

sharedYYTRequestTool = [[self alloc] init];

}

return sharedYYTRequestTool;

}

@end

　　二、用dispatch_once_t实现单例

　　1.在.h文件中

#import <Foundation/Foundation.h>

@interface YYTRequestTool : NSObject

+(id)sharedYYTRequestTool;

@end

　　2.在.m文件中

#import "YYTRequestTool.h"

@interface YYTRequestTool ()

@property(nonatomic,strong) DPAPI *api;

@end

@implementation YYTRequestTool

+(id)sharedYYTRequestTool{

static YYTRequestTool *sharedYYTRequestTool = nil;

static dispatch_once_t onceToken;

dispatch_once(&onceToken, ^{

sharedYYTRequestTool = [[self alloc] init];

});

return sharedYYTRequestTool;

}

@end