UIPickerView滚轮选择器视图

 //必须实现两个协议
 //数据源协议必须实现的两个方法
 //选取器的输出借口singlePicker,并在故事版中选择该选取器将dataSource和delegate拖入视图控制器与之关联
 //@property (weak, nonatomic) IBOutlet UIPickerView *singlePicker;
 //characterNames是自己定义的属性数组，用于往选取器中添加显示数据
 //@property (strong, nonatomic) NSArray *characterNames;
 //选取器显示几个滚轮，返回1，显示1个
 - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
     return ;
 }

 //选取器滚轮包含多少行，返回数组对象中的数量
 - (NSInteger)pickerView:(UIPickerView *)pickerView
 numberOfRowsInComponent:(NSInteger)component {

     return [self.characterNames count];
 }

 //委托协议,实现可选方法
 //使用row参数作为索引,返回数组中相应的元素
 - (NSString *)pickerView:(UIPickerView *)pickerView
              titleForRow:(NSInteger)row
             forComponent:(NSInteger)component {

     return self.characterNames[row];
 }

 //点击按钮触发事件，弹出警告框显示在选取器中选择的内容
 - (IBAction)buttonPressed:(id)sender {
     //选取器组成部分0代表第一个选取器，1则代表第二个选取器，以此类推，赋值给一个整型对象 row
     NSInteger row = [self.singlePicker selectedRowInComponent:];
     //获取数组中的内容并赋值给字符串对象selected
     NSString *selected = self.characterNames[row];
     NSString *title = [NSString stringWithFormat:@"You selected %@",selected];

     UIAlertController *singleAlert = [UIAlertController alertControllerWithTitle:title message:@"thank you for choosing" preferredStyle:UIAlertControllerStyleAlert];

     UIAlertAction *singleAction = [UIAlertAction actionWithTitle:@"Yes I did" style:UIAlertActionStyleDefault handler:nil];

     [singleAlert addAction:singleAction];

     [self presentViewController:singleAlert animated:YES completion:nil];