这要看你如何去保留的数据。举一个例子，如果你有数组作为字典的键的值，并且该字典具有不同的这样的键，所述第一列将是键，并选择一你将被显示在其他列的阵列（组分）。 - （NSInteger的）numberOfComponentsInPickerView：（UIPickerView *）pickerView 方法应返回2。
在
  - （NSInteger的）pickerView：（UIPickerView *）pickerView numberOfRowsInComponent：（NSInteger的）组件
方法，则需要给键的数量在字典组件1，并且当前选择的键的阵列的计数。
例如：

It depends on how you are going to keep data. For an example if you have an array as the value of a key of a dictionary, and that dictionary have different such keys, the first column will be the keys, and on selecting one you will be displaying the array in the other column (component). - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView method should return 2. In - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component method, you need to give the number of keys in dictionary for component 1, and count of the array of the currently selected key. eg

if(component==0) return [[DICTIONARY allKeys] count];
else return [[DICTIONARY objectForKey:@"SELECTED_KEY"] count];

然后，

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {

    selectedIndex = [pickerView selectedRowInComponent:0];
    if (component == 1 && !(selectedIndex < 0)) {
        [pickerView reloadComponent:2];

        [pickerView selectRow:0 inComponent:2 animated:YES];
    }

}

和

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view {

    UILabel *pickerRow = (view != nil) ? view : [[[UILabel alloc] initWithFrame:CGRectMake(5, 0, 115, 60)] autorelease];
    pickerRow.font = [UIFont boldSystemFontOfSize:14];
    pickerRow.textAlignment = UITextAlignmentLeft;
    pickerRow.backgroundColor = [UIColor clearColor];
    pickerRow.textColor = [UIColor blackColor];
    pickerRow.numberOfLines = 0;
    if (component == 0) {

        pickerRow.text = @"DICTIONARY_ROW'th_KEY";
    }
    else {

        pickerRow.text = [[dictionary objectForKey:@"SELECTED_KEY"] objectAtIndex:row];

    }
    return pickerRow;
}