IOS中计算文件的大小

通常用于删除缓存的时，计算缓存大小
//单个文件的大小
- ( long long ) fileSizeAtPath:(NSString*) filePath{
    NSFileManager* manager = [NSFileManager defaultManager];
    if ([manager fileExistsAtPath:filePath]){
        return [[manager attributesOfItemAtPath:filePath error:nil] fileSize];
    }
    return 0 ;
}
//遍历文件夹获得文件夹大小，返回多少M
- ( float ) folderSizeAtPath:(NSString*) folderPath{
    NSFileManager* manager = [NSFileManager defaultManager];
    if (![manager fileExistsAtPath:folderPath]) return 0 ;
    NSEnumerator *childFilesEnumerator = [[manager subpathsAtPath:folderPath] objectEnumerator];
    NSString* fileName;
    long long folderSize = 0 ;
    while ((fileName = [childFilesEnumerator nextObject]) != nil){
        NSString* fileAbsolutePath = [folderPath stringByAppendingPathComponent:fileName];
        folderSize += [self fileSizeAtPath:fileAbsolutePath];
    }
    return folderSize/( 1024.0 * 1024.0 );
}