iOS single case

#import <Foundation/Foundation.h> @interface fucardsettings:nsobject+ (fucardsettings *) sharedinstance; @end

#import   "FuCardSettings.h" @implementation  FuCardSettings//=================  single Case  =========== === startstatic fucardsettings *sharedsettings = nil;+  (FuCardSettings *) Sharedinstance {        if (sharedsettings  ==   nil) {            sharedsettings =  [[[self alloc] init]autorelease];          }     return  sharedsettings;} +  (ID) Allocwithzone: (nszone *) zone {     @synchronized (self)  {         if  (Sharedsettings == nil)  {             sharedsettings = [super allocwithzone: Zone];        }    }&nBsp;   return sharedsettings;} +  (ID) Copywithzone: (nszone *) zone {    return self;} -  (ID) retain {    return self;} -  (Nsuinteger) Retaincount {    return nsuintegermax;} -  (oneway void) release {}-  (ID) autorelease {    return self;} =================  Single Case  ============== end@end

The above is a traditional single case:

There is also a single example that is implemented with GCD:

 #import  <foundation/foundation.h>@ Interface tool1 : nsobject@property (nonatomic,copy) nsstring *test;+  (instancetype) instance, @end @implementation tool1+  (instancetype) instance{    static tool1 * tool;    static dispatch_once_t oncetoken;     Dispatch_once (&oncetoken, ^{        tool = [[tool1  alloc] init];            });     return tool;} -  (instancetype) init{    self = [super init];     if  (self)  {        _test = @ "test";     }    return self;} @end 

The notation has the following characteristics:

1. Thread safety.

2. Meet the requirements of the static analyzer.

3. Compatible with ARC

iOS single case