第一種方法：笨方法

-(NSMutableArray*)getRandomArrFrome:(NSArray*)arr
{
    NSMutableArray *newArr = [NSMutableArray new];
    while (newArr.count != arr.count) {
        //生成隨機數
        int x =arc4random() % arr.count;
        id obj = arr[x];
        if (![newArr containsObject:obj]) {
            [newArr addObject:obj];
        }
    }
    return newArr;
}
 

第二種方法：蘋果官方方法

    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];
        }
    }];