iOS 学会使用通知（notification）

继之间我们讲的delegate和block之后，今天我们一块来研讨一下notification,在实际开发中，我一般很少用到通知，因为如果项目中大量用到通知的话，就会大大降低效率，除非万不得已，跨界面之间的传递，因为notificationcenter就是一个单例，所以可以全局使用，也就是说只有在这个时候，我才会用到通知，下边我给一个demo，具体实现的现象就是我创建了三个controller，firstViewController,secondViewController,ThirdViewController,其中第二个界面就是一个起一个push的效果，为了能清晰的证明，通知可以跨界面之间进行传值（传事件），在firstViewController中注册一个观察者,并写一个弹窗事件，在thirdViewController中发送通知（在这点需要注意，那就是通知的名字一定一致，不然，肯定thirdViewController在发送通知的时候是找不到对应通知的，也就不会有回调事件了），(在需要做事情的地方发送通知，谁可以来做这件事情，谁就注册一个观察者来帮助发送这个通知的人实现这个事件)，好了，就是这样，下边是demo：

firstViewController.m

#import "FirstViewController.h"

#import "SecondViewController.h"

@interfaceFirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    self.view.backgroundColor = [UIColorbrownColor];

    UIButton *button = [UIButtonbuttonWithType:UIButtonTypeSystem];

    button.frame =CGRectMake(50,100,200,50);

    button.backgroundColor = [UIColorredColor];

    [buttonsetTitle:@"push"forState:UIControlStateNormal];

    [buttonaddTarget:selfaction:@selector(btnClick:)forControlEvents:UIControlEventTouchUpInside];

    [self.viewaddSubview:button];

    [[NSNotificationCenterdefaultCenter]addObserver:selfselector:@selector(showNotification:)name:@"notDemo"object:nil];

}

- (void)showNotification:(NSNotification *)notification {

    UIAlertController *alert = [UIAlertControlleralertControllerWithTitle:@"title"message:@"message"preferredStyle:UIAlertControllerStyleAlert];

    [alertaddAction:[UIAlertActionactionWithTitle:@"OK"style:UIAlertActionStyleDefaulthandler:nil]];

    [selfpresentViewController:alertanimated:YEScompletion:nil];

}

- (void)btnClick:(UIButton *)sender {

    SecondViewController *second = [[SecondViewControlleralloc]init];

    [self.navigationControllerpushViewController:secondanimated:YES];

}

@end

secondVIewController.m

#import "SecondViewController.h"

#import "ThirdViewController.h"

@interfaceSecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    self.view.backgroundColor = [UIColorcolorWithRed:0.5green:0.6blue:0.2alpha:YES];

    UIButton *button = [UIButtonbuttonWithType:UIButtonTypeSystem];

    button.frame =CGRectMake(50,100,200,50);

    button.backgroundColor = [UIColorredColor];

    [buttonsetTitle:@"push"forState:UIControlStateNormal];

    [buttonaddTarget:selfaction:@selector(btnClick:)forControlEvents:UIControlEventTouchUpInside];

    [self.viewaddSubview:button];

}

- (void)btnClick:(UIButton *)sender {

    ThirdViewController *third = [[ThirdViewControlleralloc]init];

    [self.navigationControllerpushViewController:thirdanimated:YES];

}

@end

thirdViewController.m

#import "ThirdViewController.h"

@interfaceThirdViewController ()

@end

@implementation ThirdViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    self.view.backgroundColor = [UIColorcolorWithRed:0.2green:0.6blue:0.5alpha:YES];

    UIButton *button = [UIButtonbuttonWithType:UIButtonTypeSystem];

    button.frame =CGRectMake(50,100,200,50);

    button.backgroundColor = [UIColorredColor];

    [buttonsetTitle:@"send notification"forState:UIControlStateNormal];

    [buttonaddTarget:selfaction:@selector(btnClick:)forControlEvents:UIControlEventTouchUpInside];

    [self.viewaddSubview:button];

}

- (void)btnClick:(UIButton *)sender {

    

    [[NSNotificationCenterdefaultCenter]postNotificationName:@"notDemo"object:niluserInfo:nil];

}

@end

好了，demo就是上边的，在第三个界面发送通知，回调第一个界面的弹窗事件。

但是使用通知就是不如代理，block那么直观，不利于代码的维护，项目中我是尽量少用