iOS 监听回调机制KVO实例

监听某个对象，如果这个对象的数据发生变化，会发送给监听者从而触发回调函数

[self.bean addobserver:self forkeypath:@"data" options:nskeyvalueobservingoptionnew|nskeyvalueobservingoptionold context:null];

这个就是注册监听，这个@“data”作为标识符方便回调函数辨认

-(void)observevalueforkeypath:(nsstring *)keypath ofobject:(id)object change:(nsdictionary *)change context:(void *)context
{
 if([keypath isequaltostring:@"data"])
 {
  self.label.text = [self.bean valueforkey:@"data"];
 }
}

这个就是回调函数，分辨是哪个对象发生变化，然后给与相应的处理

-(void)viewwilldisappear:(bool)animated{
 [self.bean removeobserver:self forkeypath:@"data"];
}

既然有注册监听还记得解除监听

以下是完整例子代码

//
// viewcontroller.m
// first
//
// created by shanreal-ios on 17/10/16.
// copyright © 2017年 shanreal.longzhenhao. all rights reserved.
//
#import "viewcontroller.h"
#import "testbean.h"
@interface viewcontroller ()
@property(nonatomic,strong)uilabel* label;
@property(nonatomic,strong)uibutton* btn;
@property(nonatomic,strong)testbean* bean;
@end
@implementation viewcontroller
- (void)viewdidload {
 [super viewdidload];
 // do any additional setup after loading the view.

 self.bean = [[testbean alloc]init];
 [self.bean setvalue:@"1" forkey:@"data"];
 
 self.label = [[uilabel alloc]initwithframe:cgrectmake(10, 30, 100, 30)];
 self.label.textcolor = [uicolor blackcolor];
 self.label.text = [self.bean valueforkey:@"data"];
 [self.view addsubview:self.label];
 
 
 self.btn = [[uibutton alloc] initwithframe:cgrectmake(10, 100, 200, 30)];
 [self.btn settitlecolor:[uicolor blackcolor] forstate:uicontrolstatenormal];
 [self.btn settitle:@"chanage data" forstate:uicontrolstatenormal];
 [self.btn addtarget:self action:@selector(clickaction) forcontrolevents:uicontroleventtouchupinside];
 [self.view addsubview:self.btn];
 
}
-(void)viewwillappear:(bool)animated{
 [self.bean addobserver:self forkeypath:@"data" options:nskeyvalueobservingoptionnew|nskeyvalueobservingoptionold context:null];
 
}
-(void)clickaction{
 int data = [[self.bean valueforkey:@"data"] intvalue]+1;
 self.bean.data = [nsstring stringwithformat:@"%d",data];
}
-(void)observevalueforkeypath:(nsstring *)keypath ofobject:(id)object change:(nsdictionary *)change context:(void *)context
{
 if([keypath isequaltostring:@"data"])
 {
  self.label.text = [self.bean valueforkey:@"data"];
 }
}
-(void)viewwilldisappear:(bool)animated{
 [self.bean removeobserver:self forkeypath:@"data"];
}

@end

#import <foundation/foundation.h>
@interface testbean : nsobject{
 nsstring* data;
}
@property(nonatomic,assign)int id;
@property(nonatomic,strong)nsstring* data;
@end

#import "testbean.h"
@implementation testbean
@end

以上这篇ios 监听回调机制kvo实例就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持。