NSString *str = @"a,b,c,d,e,f";
    NSArray *array = [str componentsSeparatedByString:@","];
    // 数组转字符串：
    NSArray *array1 = @[@"a",@"b",@"c",@"d"];
    NSString *str1 = [array1 componentsJoinedByString:@","];
    NSLog(@"array = %@", array);
    NSLog(@"str1 = %@", str1);