iOS清除缓存

//清缓存提示框
 NSString *message =  [NSString stringWithFormat:@"可清除大小%.2fM",[self folderSizeAtPath:[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject]]];
 UIAlertController * al = [UIAlertController alertControllerWithTitle:@"提示" message:message preferredStyle:UIAlertControllerStyleAlert];
 UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
 [self clearCache:[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject]];
            }];
[al addAction:okAction];
UIAlertAction *okAction2 = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            }];
[al addAction:okAction2];
[self presentViewController:al animated:YES completion:^{
        }];

#pragma mark--计算缓存的大小
/**
 *  所有的缓存调用的计算大小
 */
-(float)folderSizeAtPath:(NSString *)path{
NSFileManager *fileManager=[NSFileManager defaultManager];
float folderSize;
if ([fileManager fileExistsAtPath:path]) {
    NSArray *childerFiles=[fileManager subpathsAtPath:path];
    for (NSString *fileName in childerFiles) {
        NSString *absolutePath=[path stringByAppendingPathComponent:fileName];
        folderSize +=[self fileSizeAtPath:absolutePath];
    }
    //SDWebImage框架自身计算缓存的实现
    folderSize+=[[SDImageCache sharedImageCache] getSize]/1024.0/1024.0;
    return folderSize;
 }
  return 0;
}
/**
 *  和上面的是连贯在一起的
 */
-(float)fileSizeAtPath:(NSString *)path{
NSFileManager *fileManager=[NSFileManager defaultManager];
if([fileManager fileExistsAtPath:path]){
    long long size=[fileManager attributesOfItemAtPath:path error:nil].fileSize;
    return size/1024.0/1024.0;
  }
 return 0;
}
#pragma mark--清除缓存
-(void)clearCache:(NSString *)path{
  NSFileManager *fileManager=[NSFileManager defaultManager];
  if ([fileManager fileExistsAtPath:path]) {
    NSArray *childerFiles=[fileManager subpathsAtPath:path];
    for (NSString *fileName in childerFiles) {
        //如有需要，加入条件，过滤掉不想删除的文件
        NSString *absolutePath=[path stringByAppendingPathComponent:fileName];
        [fileManager removeItemAtPath:absolutePath error:nil];
      }
  }
  [[SDImageCache sharedImageCache] cleanDisk];
}