一般セレクタ(IOS開発)

-通常のセレクタは、委任プロトコルとデータ・ソース・プロトコルの2つのプロトコルを満たす必要があります.
-委任プロトコルはコントロールUI、イベント応答を制御し、オプションを実現する
-データソースプロトコルはコントロールとデータモデルの適用の橋渡しを担当し、一般的に実現しなければならない.
@interface ViewController : UIViewController

//
//  ViewController.h
//  PickViewSample
//
//  Created by     on 14-10-21.
//  Copyright (c) 2014     . All rights reserved.
//

#import 

@interface ViewController : UIViewController

//               ，       ，        
//           UI、    ,     
//                    ，      
@property (weak, nonatomic) IBOutlet UIPickerView *pickerView;

@property (weak, nonatomic) IBOutlet UILabel *label;


@property (nonatomic, strong) NSDictionary *pickerData;     //       
@property (nonatomic, strong) NSArray *pickerProvincesData; //      
@property (nonatomic, strong) NSArray *pickerCitiesData;    //          


- (IBAction)onclick:(id)sender;
@end

//
//  ViewController.m
//  PickViewSample
//
//  Created by     on 14-10-21.
//  Copyright (c) 2014     . All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    //                
    NSBundle *bundle = [NSBundle mainBundle];
    NSString *plistPath = [bundle pathForResource:@"provinces_cities"
                                           ofType:@"plist"];
    
    //               
    NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile: plistPath];
    self.pickerData = dict;
    
    //    
    self.pickerProvincesData = [self.pickerData allKeys];
    
    //                
    NSString *seletedProvince = [self.pickerProvincesData objectAtIndex: 0];
    // objectforkey:        
    self.pickerCitiesData = [self.pickerData objectForKey:seletedProvince];
    

    self.pickView.dataSource = self;

    self.pickView.delegate = self;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)onclick:(id)sender {
    //          0  
    NSInteger row1 = [self.pickerView selectedRowInComponent:0];
    NSInteger row2 = [self.pickerView selectedRowInComponent:1];
    NSString *selected1 = [self.pickerProvincesData objectAtIndex:row1];
    NSString *selected2 = [self.pickerCitiesData objectAtIndex:row2];
    
    NSString *title = [[NSString alloc] initWithFormat:@"%@, %@ ", selected1, selected2];
    self.label.text = title;
}

#pragma mark     UIpickerViewDataSource  
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    //            
    return 2;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    //              
    if (component == 0) {
        //       
        return [self.pickerProvincesData count];
    }
    else
    {
        //       
        return [self.pickerCitiesData count];
    }
}

#pragma mark     UIPickerViewDelegate  
//                  
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    if (component == 0) {
        //      
        return [self.pickerProvincesData objectAtIndex:row];
    }
    else
    {
        return [self.pickerCitiesData objectAtIndex:row];
    }
}
//            ，  
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    if (component == 0) {
        NSString *seletedProvince = [self.pickerProvincesData objectAtIndex:row];
        NSArray *array = [self.pickerData objectForKey:seletedProvince];
        self.pickerCitiesData = array;
        //   
        [self.pickerView reloadComponent:1];
    }
}

@end

委託とデータソースの実装オブジェクトViewControlがUIPCkerViewに割り当てた委託属性Delegateとデータソース属性dataSourceについて.
この部分はInterfaceBuilderで実現でき、割り当ては自動的に生成されます
-(void) viewDidLoad
{
...
self.pickerView.dataSource = self;
self.pickerView.delegate = self;
}