NSCache缓存机制

NSCache相关查了一些资料，没有找到核心思想的阐述，自己试验了下，验证了NSCache使用了LRU缓存算法策略。

在这里不再说明NSCache一些调用API和代理回调相关基础知识，直接贴代码。

NSCache *cache = [NSCache new];

cache.delegate=self;

cache.countLimit = 5;

[cache setObject:@"1" forKey:@"1"];

[cache setObject:@"2" forKey:@"2"];

[cache setObject:@"3" forKey:@"3"];

[cache setObject:@"4" forKey:@"4"];

[cache setObject:@"5" forKey:@"5"];

[cache setObject:@"6" forKey:@"6"];

sleep(2);

[cache objectForKey:@"2"];

[cache setObject:@"7"forKey:@"7"];

sleep(2);

[cache setObject:@"8"forKey:@"8"];

//当缓存中的一个对象即将被删除时会回调该方法

- (void)cache:(NSCache*)cachewillEvictObject:(id)obj {

NSLog(@"Remove Object %@", obj);

}

以下是打印：

2020-07-02 17:05:17.344311+0800 int[34442:1168078] Remove Object 1

2020-07-02 17:05:19.345237+0800 int[34442:1168078] Remove Object 3

2020-07-02 17:05:21.345610+0800 int[34442:1168078] Remove Object 4