如果要使用UIPickerView来获取此代码，则将选择器视图的第一个component作为空值传递，否则可以使用custom pickerview.

If you want to get this one by using UIPickerView then pass the first component of the picker view as a empty value,otherwise you can use custom pickerview.

[pickerArray addObject:@""];//first element of the picker component.