ios之NSCache的使用

#import "ViewController.h"

@interface ViewController () <NSCacheDelegate>

/// 全局的缓存池

@property (nonatomic,strong)NSCache *cache;

@end

@implementation ViewController

- (NSCache *)cache

{

    if (_cache ==nil) {

        _cache = [[NSCachealloc] init];

        

        _cache.delegate =self;

        

        // 设置缓存的个数(限额)

        _cache.countLimit =5;

    }

    return_cache;

}

- (void)viewDidLoad {

    [superviewDidLoad];

    

    // 循环的向cache中添加对象

    for (int i =0; i < 10; i++) {

        NSString *str = [NSStringstringWithFormat:@"hello_%d",i+1];

        NSLog(@"添加 %@",str);

        NSString *key = [NSStringstringWithFormat:@"key_%d",i];

        

        [self.cachesetObject:str forKey:key];

    }

    

    // 循环的取值

    for (int i =0; i < 10; i++) {

        NSString *key = [NSStringstringWithFormat:@"key_%d",i];

        NSString *str = [self.cacheobjectForKey:key];

        NSLog(@"获取 %@",str);

    }

}

/// NSCache的代理方法,在对象将要从cache中移除的时候调用的

- (void)cache:(NSCache *)cache willEvictObject:(id)obj

{

    NSLog(@"移除 %@",obj);

}

/// 在 didReceiveMemoryWarning方法中,移除了所有对象之后,再去做添加的操作

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event

{

    for (int i =0; i < 10; i++) {

        NSString *str = [NSStringstringWithFormat:@"hello_%d",i+1];

        NSLog(@"touchesBegan添加 %@",str);

        NSString *key = [NSStringstringWithFormat:@"key_%d",i];

        

        [self.cachesetObject:str forKey:key];

    }

    

    // 循环的取值

    for (int i =0; i < 10; i++) {

        NSString *key = [NSStringstringWithFormat:@"key_%d",i];

        NSString *str = [self.cacheobjectForKey:key];

        NSLog(@"touchesBegan获取 %@",str);

    }

}

/// 此时会再重新的添加

- (IBAction)clickBtn:(id)sender

{

    [self.cacheremoveAllObjects];

}

- (void)didReceiveMemoryWarning {

    [superdidReceiveMemoryWarning];

    

    // 注意 :一旦在 didReceiveMemoryWarning 调用移除全部对象的方法之后,那么这个cache永远不会再去添加对象

    [self.cacheremoveAllObjects];

}