单例模式

最新推荐文章于 2025-01-06 18:04:26 发布

原创最新推荐文章于 2025-01-06 18:04:26 发布 · 184 阅读

0 ·

CC 4.0 BY-SA版权

本文介绍了一个使用Objective-C实现的单例模式案例。通过dispatch_once确保线程安全地初始化单例对象，并重写allocWithZone及copyWithZone方法来保证无论何时请求此类的实例都返回同一个对象。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

#import "Singleton.h"

@implementation Singleton
static Singleton* _instance = nil;
+(instancetype) shareInstance
{
    static dispatch_once_t onceToken ;
    dispatch_once(&onceToken, ^{
    _instance = [[super allocWithZone:NULL] init] ;
}) ;
return _instance ;
}

+(id) allocWithZone:(struct _NSZone *)zone
{
    return [Singleton shareInstance] ;
}

-(id) copyWithZone:(struct _NSZone *)zone
{
    return [Singleton shareInstance] ;
}
@end

Singleton* obj1 = [Singleton shareInstance] ;
NSLog(@"obj1 = %@.", obj1) ;

Singleton* obj2 = [Singleton shareInstance] ;
NSLog(@"obj2 = %@.", obj2) ;

Singleton* obj3 = [[Singleton alloc] init] ;
NSLog(@"obj3 = %@.", obj3) ;

2017-03-06 15:59:51.790 Sqlite3[3068:1369867] obj1 = <SqliteTool: 0x608000010660>.
2017-03-06 15:59:51.790 Sqlite3[3068:1369867] obj2 = <SqliteTool: 0x608000010660>.
2017-03-06 15:59:51.791 Sqlite3[3068:1369867] obj3 = <SqliteTool: 0x608000010660>.