iOS--页面间的代理传值（属性、代理（委托）、代码块、单例、通知）

（一）属性传值

（二）代理（委托）传值

---

代理传值

适用于 反向传值 (从后往前传)

1.1 创建协议 及协议方法 在反向传值的页面（SecondViewController）中
1.2 创建协议类型的属性 在SecondViewController中创建属性id<postValueDelegate> delegate
1.3 调用属性 即delegate
在SecondViewController页面中 对象传值的方法中调用
[self.delegate postValue:self.textName.text];
1.4 在第一页 即显示修改过信息的页面
遵循协议 实现协议方法 指定代理对象（即 在页面传值参数的方法中为代理赋值）
secondVc.delegate=self；

文件目录：

FirstViewController.h

#import <UIKit/UIKit.h>
#import "SecondViewController.h"
@interface FirstViewController : UIViewController<UITextFieldDelegate,postValue>

@property(strong,nonatomic) UITextField *textName;
@property(strong,nonatomic) UIButton *nextbutton;

@end

FirstViewController.m

#import "FirstViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor=[UIColor redColor];
    self.textName=[[UITextField alloc] initWithFrame:CGRectMake(, , ,)];
    self.textName.borderStyle=UITextBorderStyleLine;
    self.textName.delegate=self;
    [self.view addSubview:self.textName];

    self.nextbutton=[[UIButton alloc] initWithFrame:CGRectMake(, , , )];
    [self.nextbutton setTitle:@"下一页" forState:UIControlStateNormal];
    self.nextbutton.backgroundColor=[UIColor grayColor];
    [self.nextbutton addTarget:self action:@selector(nextPage) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.nextbutton];

}

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    if ([textField isFirstResponder]) {
        [textField resignFirstResponder];
    }

    return YES;
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    [self.textName resignFirstResponder];
}

-(void)nextPage
{
    SecondViewController *secondVc=[[SecondViewController alloc] init];
    secondVc.str=self.textName.text;
    secondVc.deletage=self;
    [self presentViewController:secondVc animated:YES completion:nil];
}

-(void)postValue:(NSString *)str
{
    self.textName.text=str;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

SecondViewController.h

#import <UIKit/UIKit.h>

// 创建协议

@protocol postValue <NSObject>

-(void)postValue:(NSString *)str;

@end

@interface SecondViewController : UIViewController<UITextFieldDelegate>

@property(strong,nonatomic) UITextField *textInfo;
@property(strong,nonatomic) UIButton *backbutton;
@property(strong,nonatomic) NSString *str;

@property(strong,nonatomic) id<postValue> deletage;

@end

SecondViewController.m

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor=[UIColor colorWithRed:0.541 green:0.878 blue:0.831 alpha:1.000];

    self.textInfo=[[UITextField alloc] initWithFrame:CGRectMake(, , , )];
    self.textInfo.borderStyle=UITextBorderStyleLine;
    self.textInfo.text=self.str;
    self.textInfo.delegate=self;

    [self.view addSubview:self.textInfo];

    self.backbutton=[[UIButton alloc] initWithFrame:CGRectMake(, , , )];
    [self.backbutton setTitle:@"上一页" forState:UIControlStateNormal];
    self.textInfo.text=self.str;
    [self.backbutton addTarget:self action:@selector(backPage) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.backbutton];

}

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    if ([textField isFirstResponder]) {
        [textField resignFirstResponder];
    }

    return YES;
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    [self.textInfo resignFirstResponder];
}

-(void)backPage
{
    if (self.deletage!=) {
        [self.deletage postValue:self.textInfo.text];
    }

    [self dismissViewControllerAnimated:YES completion:nil];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

AppDelegate.h

#import <UIKit/UIKit.h>
#import"FirstViewController.h"
@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

AppDelegate.m

#import "AppDelegate.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    FirstViewController *firstVc=[[FirstViewController alloc] init];

    self.window.rootViewController=firstVc;

    return YES;
}
.......

@end

（三）代码块传值

（四）通知传值

（五）单例传值