• 首先计算缓存值的大小

//计算缓存值得大小
            float tmpSize = 0;
            NSString *diskCachePath= [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
            NSDirectoryEnumerator *fileEnumrator = [[NSFileManager defaultManager] enumeratorAtPath:diskCachePath];
            for (NSString *fileName in fileEnumrator) {
                NSString *filePath = [diskCachePath stringByAppendingPathComponent:fileName];
                NSDictionary *attrs = [[NSFileManager defaultManager] attributesOfItemAtPath:filePath error:nil];
                unsigned long long length = [attrs fileSize];
                tmpSize += length/1024.0/1024.0;
            }
            NSLog(@"tmp size is %.2f",tmpSize);
            self.tempLabel.text = [NSString stringWithFormat:@"%.2fM",tmpSize];

• 清除缓存

 //执行清除缓存操作.放在子线程中进行.
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
                NSString *cachPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
                NSArray *files = [[NSFileManager defaultManager] subpathsAtPath:cachPath];
                NSLog(@"files:%ld",(unsigned long)[files count]);
                
                for (NSString *p in files) {
                    NSError *error;
                    NSString *path = [cachPath stringByAppendingPathComponent:p];
                    if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
                        [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
                    }
                }
                [self performSelectorOnMainThread:@selector(clearCachesSuccess) withObject:nil waitUntilDone:YES];
            });

//清楚缓存
- (void)clearCachesSuccess{
    
    [self myAlertMessage:@"是否清除缓存"];
}

#pragma mark------提示框
- (void)myAlertMessage:(NSString*)message{
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"友情提示" message: message preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *sureAction = [UIAlertAction actionWithTitle:@"确定" style: UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        // 开始清空
        self.tempLabel.text = @"";
        NSLog(@"清除成功");
    }];
    UIAlertAction *cancelACtion = [UIAlertAction actionWithTitle:@"取消" style: UIAlertActionStyleDefault handler:nil];
    [alertController addAction:sureAction];
    [alertController addAction:cancelACtion];
    [self presentViewController:alertController animated:YES completion:nil];
}