objective-C学习 sigton单例

#import <Foundation/Foundation.h>

#import "UserContext.h"

int main(int argc,const char * argv[]) {

    @autoreleasepool {

        UserContext *userContext = [UserContextshareUserContext];

        UserContext *userContext2 = [UserContextshareUserContext];

        UserContext *userContext3 = [[UserContextalloc]init];

        UserContext *userContext4 = [userContextcopy];

        UserContext *userContext5 = [userContextcopy];

        [userContext retain];

        [userContext release];

        [userContext release];

        [userContext release];

        NSLog(@"");

    }

    return 0;

}

#import <Foundation/Foundation.h>

@interface UserContext : NSObject<NSCopying>

@property (nonatomic,copy)NSString *userName;

@property (nonatomic,copy)NSString *email;

+ (id)shareUserContext; //单例命名习惯前缀：share或default关键字

@end

#import "UserContext.h"

static UserContext *segtonInstance =nil;

@implementation UserContext

+ (id)shareUserContext

{

    @synchronized(self)  //线程保护

    {

        if (segtonInstance ==nil)

        {

        segtonInstance = [[[selfclass]alloc]init];

        }

    }

    returnsegtonInstance;

}

//下面方法为了确保一个实例

+ (id)allocWithZone:(struct_NSZone *)zone{

    if (segtonInstance ==nil) {

        segtonInstance = [superallocWithZone:zone];

    }

    returnsegtonInstance;

}

- (id)copyWithZone:(nullableNSZone *)zone {

    returnsegtonInstance;

}

- (id)retain{

    returnsegtonInstance;

}

- (oneway void)release{

}

- (id)autorelease{

    returnsegtonInstance;

}

-(NSUInteger)retainCount{

    returnUINT_MAX;

}

@end