iOS 之缓存类NSCache的使用

首先实现缓存类的delegate <NSCacheDelegate>
@property (nonatomic, strong) NSCache *cache;

初始化缓存类NSCache

- (NSCache *)cache {
    if (_cache == nil) {
        _cache = [[NSCache alloc] init];
        //缓存中总共可以存储多少条
        _cache.countLimit = 5;
    }
    return _cache;
}

然后设置delegate,往NSCache里面添加数据

 
    //添加缓存数据
    for (int i = 0; i < 10; i++) {
        [self.cache setObject:[NSString stringWithFormat:@"hello %d",i] forKey:[NSString stringWithFormat:@"h%d",i]];
        NSLog(@"添加 %@",[NSString stringWithFormat:@"hello %d",i]);
    }
    
    //输出缓存中的数据
    for (int i = 0; i < 10; i++) {
        NSLog(@"%@",[self.cache objectForKey:[NSString stringWithFormat:@"h%d",i]]);
    }

//将要从NSCache中移除一项的时候执行
- (void)cache:(NSCache *)cache willEvictObject:(id)obj {
    NSLog(@"从缓存中移除  %@",obj);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self.cache removeAllObjects];
    
    //添加缓存数据
    for (int i = 0; i < 10; i++) {
        [self.cache setObject:[NSString stringWithFormat:@"hello %d",i] forKey:[NSString stringWithFormat:@"h%d",i]];
//        NSLog(@"添加 %@",[NSString stringWithFormat:@"hello %d",i]);
    }
    
    //输出缓存中的数据
    for (int i = 0; i < 10; i++) {
        NSLog(@"%@",[self.cache objectForKey:[NSString stringWithFormat:@"h%d",i]]);
    }

}