Single-instance mode for IOS development

The singleton is that project is only initialized once, saving memory space. or share resources. For example, when creating a Bluetooth class, or to do WiFi communication is often used. can also be used to pass values.

Introduce two ways to create a single case

One, consider the wording of thread safety

/** *  Consider thread-safe notation * *  @return  Modeltool object */+ (instancetype) sharemodel{    static Modeltool *model = nil;    Static dispatch_once_t Oncetoken;    Dispatch_once (&oncetoken, ^{        model = [[Self alloc] init];    });    return model;}

Two, do not consider the thread-safe wording

/** *  do not consider thread-safe notation * *  @return Modeltool object */+ (instancetype) sharemodeltool{    static Modeltool *model = nil;    if (!model) {        model = [[Modeltool alloc] init];    }    return model;}

Three, test these two kinds of wording

-(void) viewdidload {    [super viewdidload];   1.0 consider thread-safe    modeltool *tool1 = [Modeltool Sharemodel];    Modeltool *tool2 = [Modeltool Sharemodel];    Modeltool *tool3 = [Modeltool Sharemodel];    NSLog (@ "tool1 = =%@ Tool2 = =%@ Tool3 =%@", tool1,tool2,tool3);    2.0 do not consider thread safety    modeltool *t1 = [Modeltool sharemodeltool];    Modeltool *t2 = [Modeltool sharemodeltool];    Modeltool *t3 = [Modeltool sharemodeltool];    NSLog (@ "T1 = =%@ T2 = =%@ T3 =%@", t1,t2,t3);}

Four. Print results

2016-03-08 14:26:43.996 Single case design mode [2144:779656] tool1 = = <ModelTool:0x7fb3f1412d20> Tool2 = = <modeltool: 0x7fb3f1412d20> Tool3 = = <ModelTool:0x7fb3f1412d20>     2016-03-08 14:26:43.997 single case design mode [2144:779656] T1 = = <ModelTool:0x7fb3f15263d0> t2 = = <ModelTool:0x7fb3f15263d0> T3 = = <ModelTool:0x7fb3f15263d0>

Both methods guarantee that a piece of memory space is created.

Single-instance mode for IOS development