IOS. Common design Patterns. 01. Singleton Mode

Classes that use Singleton mode:

UIApplication

Uiaccelerometer

Nsuserdefaults

Nsnotificationcenter

Nsfilemanager

NSBundle, etc.

Singleton.h

#import <Foundation/Foundation.h>@interface  singleton:nsobject//  Always return the same Singleton pointer + (Singleton **singletondata; @end

Singleton.m

#import "Singleton.h"@implementationSingleton@synthesizeSingletondata =_singletondata;StaticSingleton *sharemanger =Nil;/** This method uses the GCD (Grand Central Dispatch) technology, which is an opportunity for the C-language multi-threaded access count. The Dispatch_once function is provided by GCD, and its purpose is to execute only one block of code throughout the application life cycle. Dispatch_once_t is a struct provided by GCD, which is used to pass the GCD address to the Dispatch_once function. The Dispatch_once function can record whether the code is being called quickly or not. **/+ (Singleton *) sharedmanager{Staticdispatch_once_t once; Dispatch_once (&once, ^{Sharemanger=[[Self alloc] init];    }); returnSharemanger;}@end

Singleappdelegate

-(BOOL) Application: (UIApplication *) application didfinishlaunchingwithoptions: (nsdictionary *) launchOptions{     @" Singleton Init " ;         *bundle = [NSBundle mainbundle];    NSLog (@ "bundle =%@", bundle);     return YES;}

Singleviewcontroller.m

-(void) viewdidload{    [Super Viewdidload];        NSLog (@ "viewdidload Print:%@", [Singleton sharedmanager].singletondata);     *bundle = [NSBundle mainbundle];    NSLog (@ "bundle =%@", bundle);}