iOS开发中 代理，block，KVO 的使用

1.代理
IPView.h
@protocol TPViewDelegate <NSObject>
- (void)IPView:(UIView*)view finishEdit:(NSString *)text;
@end
@interface IPView : UIView <UITextFieldDelegate>
@property (nonatomic,assign)id<TPViewDelegate> delegate;
@end
IPView.m
- (void)pushMessage{
    [_textView endEditing:YES];
    if (str!= nil) {
        [self.delegateIPView:self finishEdit:str];
    }
    self.hidden= YES;
}
ViewController.m
- (void)IPView:(UIView*)view finishEdit:(NSString *)text{
    self.label.text= text;
}

2.闭包

BLView.h

typedefvoid(^textBlock)(NSString *);

@interfaceBLView : UIView <UITextFieldDelegate>
@property (nonatomic,copy)textBlockmyTextBlock;
@end

BLView.m
- (void)pushMessage{
    [_textView endEditing:YES];
    if (self.str!= nil) {
        self.myTextBlock(self.str);
    }
    self.hidden= YES;
}

ViewController.m
    _BLView.myTextBlock= ^(NSString *str){
         self.label.text= str;
    };


3.KVO
BLView.h
#import <UIKit/UIKit.h>
@interface BLView : UIView <UITextFieldDelegate>
@property (nonatomic,copy)NSString*str;
@end

ViewController.m
- (void)viewDidLoad {
    [super viewDidLoad];
...
          /**
     *  被观察者
     *
     *  @param NSObject 观察者
     *  @param KeyPath 被观察的属性路径
     *  @param options 返回的值的类型
     {    NSKeyValueObservingOptionNew = 0x01,  变化之后的值
          NSKeyValueObservingOptionOld = 0x02,  变化之前的值
     }
     *  @param context 一般写nil
     *
     */
    [_BLView addObserver:selfforKeyPath:@"str"options:NSKeyValueObservingOptionNewcontext:nil];
}
// 观察者的方法
/**
 *  当观察者 监视的属性发生变化时候调用的方法
 *
 *  @param keyPath 观察的属性
 *  @param object  被观察的对象
 *  @param change  属性的值
 *  @param context nil
 */
- (void)observeValueForKeyPath:(NSString*)keyPath ofObject:(id)object change:(NSDictionary*)change context:(void *)context{
    self.label.text= change[@"new"];

}