1、介绍
对象之间需要相互通信，一种名叫“委托模式”的编程设计模式来实现对象之间的通信。
该模式主旨是：定义一套接口，某对象若想接受另一个对象的委托，则需要遵从此接口，以便成为其“委托对象”（delegate）。而这“另一个对象”则可以给其委托对象回传一些信息，也可以在发生相关事件时通知委托对象。
该模式可以将数据与业务逻辑解耦。比如一个显示一系列数据所用的视图，这个视图对象的属性中，可以包含负责数据与事件处理的对象，这两种对象分别称为“数据源”（data source）与“委托”（delegate）。
实现委托对象：声明某个类遵从委托协议，然后把协议中想实现的方法在类中实现出来。某个类若遵从委托协议，可以在接口中声明，也可以在class-continuation分类中声明，一般都是在class-continuation分类里声明。
当某对象需要从另外一个对象中获取数据时，可以使用委托模式，在这种情境下，该模式也可以称为“数据源协议”（data source protocal）。
2、选择器 DataPicher
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
[self.myDatapick addTarget:self action:@selector(onDataChange:) forControlEvents: UIControlEventValueChanged];
}
-(IBAction)onDataChange:(UIDatePicker *)dataPicker {
NSData * data = self.myDatapick.date;
NSDateFormatter * dataFormatter=[[NSDateFormatter alloc] init];
dataFormatter.dateFormat=@"YYYY-MM-dd HH:mm:ss"; //设置时间格式
NSString *dateString = [dataFormatter stringFromDate:data];
NSLog(@"formate date is:%@", dateString);
self.timeLabel.text = dateString; //label显示时间
}
@end
3、普通选择器 UIPicherView
3.1 创建plist资源文件或者导入plist文件
创建：New files > Resource > Property List 命名为provinces
创建时候注意上图的类型：dictionary、array等
3.2源码
上图三个控件：label、button、普通选择器
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@property (weak, nonatomic) IBOutlet UILabel *timeLabel;
@property (weak, nonatomic) IBOutlet UIDatePicker *myDatapick;
@property (weak, nonatomic) IBOutlet UIPickerView *picjView;
@property (weak, nonatomic) IBOutlet UIButton *button;
@end
#import "ViewController.h"
@interface ViewController ()<UIPickerViewDataSource,UIPickerViewDelegate>
@property(strong,nonatomic) NSDictionary *allData;
@property(strong,nonatomic) NSArray *level1;
@property(strong,nonatomic) NSArray *level2;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
[self.myDatapick addTarget:self action:@selector(onDataChange:) forControlEvents: UIControlEventValueChanged];
//委托协议和数据源分配
self.picjView.dataSource=self;
self.picjView.delegate=self;
[self initData];
[self.button addTarget:self action:@selector(onClickButton:) forControlEvents:(UIControlEventTouchDown)];
}
-(IBAction)onDataChange:(UIDatePicker *)dataPicker {
NSData * data = self.myDatapick.date;
NSDateFormatter * dataFormatter=[[NSDateFormatter alloc] init];
dataFormatter.dateFormat=@"YYYY-MM-dd HH:mm:ss";
NSString *dateString = [dataFormatter stringFromDate:data];
NSLog(@"formate date is:%@", dateString);
self.timeLabel.text = dateString;
}
-(IBAction)onClickButton:(id)sender{
NSInteger row1=[self.picjView selectedRowInComponent:0];
NSInteger row2=[self.picjView selectedRowInComponent:1];
NSString *selected1=[self.level1 objectAtIndex:row1];
NSString *selecter2=[self.level2 objectAtIndex:row2];
NSString *title=[[NSString alloc]initWithFormat:@"%@ | %@",selected1,selecter2];
self.timeLabel.text=title;
}
-(void) initData{
NSString *plistPath = [[NSBundle mainBundle]pathForResource:@"province" ofType:@"plist"];
NSDictionary *dictionary=[[NSDictionary alloc] initWithContentsOfFile:plistPath];
self.allData=dictionary;
self.level1=[self.allData allKeys];
NSString *selectedLevel1=[self.level1 objectAtIndex:0];
self.level2=[self.allData objectForKey:selectedLevel1];
}
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
return 2;
}
-(NSInteger)pickerView:(nonnull UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
if(component ==0){
return [self.level1 count];
}else{
return [self.level2 count];
}
}
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
if(component == 0) {
return [self.level1 objectAtIndex:row];
} else {
return [self.level2 objectAtIndex:row];
}
}
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
if(component == 0) {
NSString *seletedP1 = [self.level1 objectAtIndex:row];
NSArray *array = [self.allData objectForKey:seletedP1];
self.level2 = array;
[self.picjView reloadComponent:1];
}
}
@end
运行结果：
