單例模式－ios

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#import <Foundation/Foundation.h>@interface UserContext : NSObject <NSCopying>@property (nonatomic,copy) NSString *name;@property (nonatomic,copy) NSString *emial;+(id) shareUsercontext;@end

 

#import "UserContext.h"static UserContext *segtonInstance=nil;@implementation UserContext+(id) shareUsercontext{        @synchronized(self){            if(segtonInstance==nil){        segtonInstance=[[[self class] alloc] init];        }            }    return segtonInstance;}+(id) allocWithZone:(struct _NSZone *)zone{    if (segtonInstance==nil) {        segtonInstance=[super allocWithZone:zone];    }    return segtonInstance;}- (id)copyWithZone:(NSZone *)zone{        return segtonInstance;    }@end

 

/**單例模式***/        UserContext *usercontext=[UserContext shareUsercontext];        UserContext *usercontext2=[UserContext shareUsercontext];        UserContext *usercontext3=[[UserContext alloc] init];        UserContext *usercontext4=[usercontext copy];        NSLog(@"%p",usercontext);        NSLog(@"%p",usercontext2);        NSLog(@"%p",usercontext3);        NSLog(@"%p",usercontext4);