Singleton mode-BASIC Implementation 01

1- (void) Viewdidload2 {3 [Super Viewdidload];4     5 [self test]; 6 }7 8- (void) Test9 {TenXzmusictool *tool =[[Xzmusictool alloc] init]; OneXzmusictool *tool2 =[[Xzmusictool alloc] init]; AXzmusictool *tool3 =[Xzmusictool Sharedmusictool]; -Xzmusictool *tool4 =[Xzmusictool Sharedmusictool]; -      the         //copy has the potential to produce new objects -         //The copy method is called internally-Copywithzone: -Xzmusictool *TOOL5 =[tool4 copy]; -      +NSLog (@"%@ %@ %@ %@ %@", tool, Tool2, Tool3, Tool4, TOOL5); -}

[[Xzmusictool alloc] init];

[Xzmusictool Sharedmusictool];

[Tool4 copy];

All three of these methods guarantee that the object created is the same one.

1 .2 //Lazy Type3 4 #import "XZMusicTool.h"5 6 @implementationXzmusictool7 Static ID_instance;8 9 /**Ten * This method is called internally by the Alloc method One  */ A+ (ID) Allocwithzone: (struct_nszone *) Zone - { -     if(_instance = = nil) {//prevent frequent lock -up the @synchronized (self) { -             if(_instance = = nil) {//prevent creation of multiple -_instance =[Super Allocwithzone:zone]; -             } +         } -     } +     return_instance; A } at  -+(instancetype) Sharedmusictool - { -     if(_instance = = nil) {//prevent frequent lock -up - @synchronized (self) { -             if(_instance = = nil) {//prevent creation of multiple in_instance =[[Self alloc] init]; -             } to         } +     } -     return_instance; the } *  $- (ID) Copywithzone: (Nszone *) ZonePanax Notoginseng { -     return_instance;//now that you can copy, it means that you have created the object.  the } + @end

Make a comparison of the following code:

1 @implementationPaymanager2 3+(instancetype) Sharedmanager {
4     Staticdispatch_once_t Oncetoken;5     StaticPaymanager *_instance;
6Dispatch_once (&oncetoken, ^{7_instance =[[Paymanager alloc] init];8     });9     return_instance;Ten } One  A @end

Singleton mode-BASIC Implementation 01