iOS --随机打乱一个数组的顺序 获得一个新的数组

   NSArray* arr = @[@"1",@"2",@"3"];
    arr = [arr sortedArrayUsingComparator:^NSComparisonResult(NSString *str1, NSString *str2) {
        int seed = arc4random_uniform(2);
        if (seed) {
            return [str1 compare:str2];
        } else {
            return [str2 compare:str1];
        }