【iOS】通知传值

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//ChangeValue即为通知名称，需要与注册监听者中的通知名称保持一致
//object：需要与注册监听者中的object保持一致，除非注册监听者中的object为nil。
//userInfo：信息字典，包含了有关通知的可选信息
[[NSNotificationCenter defaultCenter]postNotificationName:@"ChangeValue" object:nil userInfo:@{@"Value":_textF.text}];

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//addObserver：监听通知的对象
//selector：监听到通知时所执行的方法
//name：通知名称，与注册通知的name保持一致
//object：由于通知的查找方式时先找监听者，再根据监听者找通知，所以object写成nil就代表可以接收使用通知发来的数据，
//但是如果写成self，就会从注册中心找self，如果注册通知写的不是self，就会找不到，所以需要注册通知的object向注册监听者的object适应
//object一般可以都写成nil，不易出错
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(ChangeTextFText:) name:@"ChangeValue" object:nil];

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//写在接收值界面也是第一界面，在完成传值后进行移除通知，防止内存泄露 
[[NSNotificationCenter defaultCenter]removeObserver:self];

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#import "ViewController.h"
#import "SecondViewController.h"
@interface ViewController ()
@property (nonatomic,strong) UITextField *textField;
@property (nonatomic,strong) UIButton *nextBtn;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
self.navigationItem.title = @"通知传值";
self.view.backgroundColor = [UIColor yellowColor];
//创建textField
_textField = [[UITextField alloc]initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, 50)];
_textField.borderStyle = UITextBorderStyleRoundedRect;
_textField.backgroundColor = [UIColor whiteColor];
//创建button
_nextBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
_nextBtn.frame = CGRectMake(20, 200, self.view.bounds.size.width - 40, 44);
_nextBtn.backgroundColor = [UIColor blueColor];
_nextBtn.titleLabel.font = [UIFont systemFontOfSize:25.0];
_nextBtn.tintColor = [UIColor whiteColor];
[_nextBtn setTitle:@"Next" forState:UIControlStateNormal];
[_nextBtn addTarget:self action:@selector(nextBtn:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:self.textField];
[self.view addSubview:self.nextBtn];
//
注册监听者
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(ChangeTextFText:) name:@"ChangeValue" object:nil];
}
-(void)ChangeTextFText:(NSNotification *)notification{
NSDictionary *dict = notification.userInfo;
NSLog(@"dict = %@",dict);
_textField.text = dict[@"Value"];
//移除通知
[[NSNotificationCenter defaultCenter]removeObserver:self];
}
//进入第二层界面即传值界面
-(void)nextBtn:(UIButton *)sender{
SecondViewController *secondVC = [[SecondViewController alloc]init];
[self presentViewController:secondVC animated:YES completion:nil];
}
@end

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#import "SecondViewController.h"
@interface SecondViewController ()
@property (nonatomic,strong) UITextField *textSecond;
@property (nonatomic,strong) UIButton *backBtn;
@end
@implementation SecondViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
[super viewDidLoad];
self.view.backgroundColor = [UIColor cyanColor];
//创建textField
_textSecond = [[UITextField alloc]initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, 50)];
_textSecond.borderStyle = UITextBorderStyleRoundedRect;
_textSecond.backgroundColor = [UIColor whiteColor];
//创建button
_backBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
_backBtn.frame = CGRectMake(20, 200, self.view.bounds.size.width-40,40);
_backBtn.backgroundColor = [UIColor blueColor];
_backBtn.tintColor = [UIColor whiteColor];
_backBtn.titleLabel.font = [UIFont systemFontOfSize:25.0];
[_backBtn setTitle:@"Back" forState:UIControlStateNormal];
[_backBtn addTarget:self action:@selector(backBtn:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:self.textSecond];
[self.view addSubview:self.backBtn];
}
-(void)backBtn:(UIButton *)sender{
//
注册通知
[[NSNotificationCenter defaultCenter]postNotificationName:@"ChangeValue" object:nil userInfo:@{@"Value":_textSecond.text}];
NSLog(@"%@",self.textSecond.text);
[self dismissViewControllerAnimated:YES completion:nil];
}
@end