作品链接：
http://www.jianshu.com/users/1e0f5e6f73f6/top_articles

1.计算文件的大小

1.方法一

 // 总大小
    unsigned long long size = 0;
    
    // 获得缓存文件夹路径
    NSString *cachesPath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject;
    NSString *dirpath = [cachesPath stringByAppendingPathComponent:@"Asd"];
    NSLog(@"%@",dirpath);
    // 文件管理者
    NSFileManager *mgr = [NSFileManager defaultManager];
    
    // 获得文件夹的大小  == 获得文件夹中所有文件的总大小 contentsOfDirectoryAtPath:  只能获取一层
        PHLog(@"contents - %@", [mgr contentsOfDirectoryAtPath:dirpath error:nil]);
    
    // subpathsAtPath 能获取子层的
    NSArray *subpaths = [mgr subpathsAtPath:dirpath];
    for (NSString *subpath in subpaths) {
        // 全路径
        NSString *fullSubpath = [dirpath stringByAppendingPathComponent:subpath];
        // 累加文件大小
        size += [mgr attributesOfItemAtPath:fullSubpath error:nil].fileSize;
        
        //        NSDictionary *attrs = [mgr attributesOfItemAtPath:fullSubpath error:nil];
        //        size += [attrs[NSFileSize] unsignedIntegerValue];
    }
    
   NSLog(@"asd = %zd",size);

2.方法二

 // 总大小
    unsigned long long size = 0;
    // 缓存路径文件夹
    NSString *cachesPath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject;
    NSString *dirpath = [cachesPath stringByAppendingPathComponent:@"default"];
    NSLog(@"%@",dirpath);
    // 文件管理者
    NSFileManager *manager = [NSFileManager defaultManager];
    
    // 获得文件夹的大小  == 获得文件夹中所有文件的总大小
    // Enumerator : 遍历器\迭代器
    
    NSDirectoryEnumerator *enumerator = [manager enumeratorAtPath:dirpath];
    
    for (NSString *subpath in enumerator ) {
        // 全路径
        NSString *fullSubpath = [dirpath stringByAppendingPathComponent:subpath];
        // 累加文件大小
        size += [manager attributesOfItemAtPath:fullSubpath error:nil].fileSize;
    }
    
    NSLog(@"%zd",size);

2.清除文件的缓存

- 宏定义

#define PHCustomCacheFile [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject stringByAppendingPathComponent:@"Custom"]

1.计算大小

- (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    if (self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]) {
        //设置cell右边的指示器(用来说明正在处理一些事情)
        
        UIActivityIndicatorView *loadingView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
        [loadingView startAnimating];
        self.accessoryView = loadingView;
        
         // 设置cell默认的文字(如果设置文字之前userInteractionEnabled=NO, 那么文字会自动变成浅灰色)
        
        self.textLabel.text = @"清除缓存(正在计算缓存大小...)";
        
        self.userInteractionEnabled = NO;
        
      // 弱引用指向对象死的时候，它指向的对象就会生成空，就不会产生野指针，不会产生坏内存访问。
        
       // __weak PHClearCacheCell *weakSelf = self;
        __weak typeof(self) weakSelf = self;
        
        // 在子线程计算缓存大小
        
        dispatch_async(dispatch_get_global_queue(0, 0), ^{
            
//#warning yanchi
//            [NSThread sleepForTimeInterval:3.0];
            // 获得缓存文件夹路径
            unsigned long long size = PHCustomCacheFile.fileSize;
            
            //unsigned long long size = @"/Users/apple/Desktop/Snip20160711_7.png".fileSize;
            
            size += [SDImageCache sharedImageCache].getSize;
            
            // 如果cell已经销毁了, 就直接返回
            if (weakSelf == nil) return ;
            
            NSString *sizeText = nil;
            if (size >= pow(10, 9)) { // size >= 1GB
                sizeText = [NSString stringWithFormat:@"%.2fGB", size / pow(10, 9)];
            } else if (size >= pow(10, 6)) { // 1GB > size >= 1MB
                sizeText = [NSString stringWithFormat:@"%.2fMB", size / pow(10, 6)];
            } else if (size >= pow(10, 3)) { // 1MB > size >= 1KB
                sizeText = [NSString stringWithFormat:@"%.2fKB", size / pow(10, 3)];
            } else { // 1KB > size
                sizeText = [NSString stringWithFormat:@"%zdB", size];
            }
            // 生成文字
            NSString *test = [NSString stringWithFormat:@"清除缓存(%@)",sizeText];
            
            //回到主线程
            dispatch_async(dispatch_get_main_queue(), ^{
                // 设置文字
                weakSelf.textLabel.text = test;
                // 清空右边的指示器
                weakSelf.accessoryView = nil;
                // 显示右边的箭头
                weakSelf.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
                
                // 添加手势监听器
                [weakSelf addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(clearCache)]];
                // 恢复点击事件
                weakSelf.userInteractionEnabled = YES;
            });
            
        });

    }
   
    return self;
}

2.清除缓存

- (void)clearCache
{
    // 弹出指示器
    [SVProgressHUD showWithStatus:@"正在清除缓存..." maskType:SVProgressHUDMaskTypeBlack];
    // 删除SDWebImage的缓存
    [[SDImageCache sharedImageCache] clearDiskOnCompletion:^{
        // 删除自定义的缓存
        dispatch_async(dispatch_get_global_queue(0, 0), ^{
            
            NSFileManager *manager = [NSFileManager defaultManager];
            [manager removeItemAtPath:PHCustomCacheFile error:nil];
            [manager createDirectoryAtPath:PHCustomCacheFile withIntermediateDirectories:YES attributes:nil error:nil];
//#warning 睡眠
  //          [NSThread sleepForTimeInterval:2.0];
            // 所有的缓存都清除完毕

            dispatch_async(dispatch_get_main_queue(), ^{
                // 隐藏指示器
                [SVProgressHUD dismiss];
                // 设置文字
                self.textLabel.text = @"清除缓存(0B)";
            });

        });
    }];
}

/**
 *  当cell重新显示到屏幕上时, 也会调用一次layoutSubviews
 */
- (void)layoutSubviews
{
    [super layoutSubviews];
    // cell重新显示的时候, 继续转圈圈
    UIActivityIndicatorView *loadingView = (UIActivityIndicatorView *)self.accessoryView;
    
    [loadingView startAnimating];
}