1. 代理传值

特点：一般用于反向传值，正向传值也可以，只不过不常用而已;
一对一

从 TwoVC 页面传值到 OneVC 页面，代码如下：

OneVC.m

@interface OneVC () <ReverseDelegate>
@end

@implementation OneVC

- (void)pushToTwoVC
{
    TwoVC *twoVC = [[TwoVC alloc] init];
    twoVC.reverseDelegate = self;
    [self.navigationController pushViewController:twoVC animated:YES];
}

#pragma mark - 逆向传值的代理
- (void)reversePassValue:(NSString *)value
{
    NSLog(@"反向传值为：%@", value);
}

@end

TwoVC.h

@protocol ReverseDelegate <NSObject>
- (void)reversePassValue:(NSString *)value;
@end

@interface TwoVC : UIViewController
@property (nonatomic, weak) id<ReverseDelegate> reverseDelegate;
@end

TwoVC.m

- (void)popToOneVC
{
    [self.reverseDelegate reversePassValue:@"I love you too."];
    [self.navigationController popViewControllerAnimated:YES];
}

2. Block 传值

特点：逆向传值
一对一

从 TwoVC 页面传值到 OneVC 页面，代码如下：

TwoVC.h

   //定义你需要的block
typedef void (^ReverseBlock_name_age) (NSString *name, NSInteger age);

@interface TwoVC : UIViewController

/** 声明一个block属性，这个block是获取传值的界面传进来的，参数为 name,age */
@property (nonatomic, strong) ReverseBlock_name_age reverseBlock_name_age;

@end

TwoVC.m

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    __weak typeof(self) weakself = self;
    weakself.name = @"panzhangbao";
    weakself.age = 25;
    
    if (_reverseBlock_name_age) {
        _reverseBlock_name_age(weakself.name, weakself.age);
    }
    [weakself.navigationController popViewControllerAnimated:YES];
}

OneVC.m

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    TwoVC *twoVC = [[TwoVC alloc] init];
        //在这里获取TwoVC传过来的值，并进行相应处理（如：打印）
    twoVC.reverseBlock_name_age = ^(NSString *name, NSInteger age){
        NSLog(@"反向Block传值为 name:%@, age:%ld", name, age);
    };
    [self.navigationController pushViewController:twoVC animated:YES];
}

3. 通知传值

特点：任意页面传值
一对多

发送通知页面

// 发送通知
  [[NSNotificationCenter defaultCenter] postNotificationName:@"reversePassValueNOTE" object:@"reversePassValueNOTE" userInfo:@{@"key":@"I love you."}];

接收通知页面 - 可以为多个页面

// 注册通知
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(getNotification:) name:nil object:@"reversePassValueNOTE"];

// 获取通知
- (void) getNotification:(NSNotification *)notificaion{
    self.textField.text = notificaion.userInfo[@“key”];
}

// 移除通知
   [[NSNotificationCenter defaultCenter] removeObserver:self name:@"reversePassValueNOTE" object:nil];

4. 单例传值

特点：一定初始化，N 次调用
一对多

首先，新建一个单例类，代码如下：

Singleton.h

#import <Foundation/Foundation.h>

@interface Singleton : NSObject

@property (nonatomic, copy) NSString *passValue;

/** 创建实例方法 */
+ (instancetype)sharedInstance;
@end

Singleton.m

#import "Singleton.h"

@implementation Singleton

// 以下代码在单例类中的.m 文件中写
static id _singleton;

/** 一般只调用这个类方法就行，返回的是类对象。当然也可以在.h 文件中定义其他单例对象 */
+ (instancetype)sharedInstance
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _singleton = [[self alloc] init];
    });
    
    return _singleton;
}

//重写allocWithZone:方法，在这里创建唯一的实例(注意线程安全)
+ (instancetype)allocWithZone:(struct _NSZone *)zone
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _singleton = [super allocWithZone:zone];
    });
    
    return _singleton;
}

- (id)copyWithZone:(NSZone *)zone
{
    return _singleton;
}
- (id)mutableCopyWithZone:(NSZone *)zone {
    return _singleton;
}

@end

首页代码进行相应的初始化和赋值，代码如下：

ViewController.m

#import "ViewController.h"
#import "OtherVC.h"
#import "Singleton.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad 
{
    [super viewDidLoad];

    Singleton *singleton = [Singleton sharedInstance];
    singleton.passValue = @"你好，单例";
    [self.navigationController pushViewController:[OtherVC new] animated:YES];
}
@end

在其他页面进行单例值的接收，代码如下：

Other.m

#import "OtherVC.h"

@interface OtherVC ()

@end

@implementation OtherVC

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    Singleton *singleton = [Singleton sharedInstance];
    NSLog(@" 获取的单例传值为：%@", singleton.passValue);
}
@end