2016-04-22

ios页面传值：正向、反向

iOS开发中，页面传值是很常见的，但是页面传值你究竟知道多少呢？笔者这篇文章就是给大家介绍一下页面传值的具体方式，有不足之处，欢迎大家指正，希望能和大家共同进步。说明一下：这里所说的正向、反向传值是指相关联的两个页面间的传值。

目前我所了解和掌握的传值方式有：属性传值、代理传值、Block传值、KVO传值、通知传值、单例传值、KVC传值。

下面我们来一一看下它们究竟是怎样进行操作和传值的呢？

假设我们现在有控制器（页面）A和控制器（页面）B，A->push->B，即A是B的上一个页面（控制器）。

属性传值
用法：正向传值
需求：当A-push到B时，B中有一个Label需要显示从A中的一个TextField输入的内容，这时我们需要用到正向传值。

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"

@interface A_ViewController ()

@property (nonatomic, strong) UITextField *aTextField;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.aTextField.layer.borderWidth = 1;
    [self.view addSubview:self.aTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

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

    /**
     什么时候可以用 属性 传值

     A 传到 B，正向传值

     B 在 A页面 提前初始化

     **/

    B_ViewController *bViewController = [[B_ViewController alloc] init];
    bViewController.string = self.aTextField.text;
    [self.navigationController pushViewController:bViewController animated:YES];

}

@end

B控制器.h文件：

#import <UIKit/UIKit.h>

@interface B_ViewController : UIViewController

@property (nonatomic, copy) NSString *string;

@end

B控制器.m文件：

#import "B_ViewController.h"

@interface B_ViewController ()

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    self.view.backgroundColor = [UIColor whiteColor];
    UILabel *bLabel = [[UILabel alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    bLabel.layer.borderColor = [UIColor grayColor].CGColor;
    bLabel.layer.borderWidth = 1;
    [self.view addSubview:bLabel];

    bLabel.text = self.string;
}

@end

代理传值
用法：反向传值：
需求：A-push到B，当B消失的时候，A中有一个Label需要显示从B中的一个TextField输入的内容，这时我们需要用到反向传值。

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"

@interface A_ViewController () <BToADelegate>

@property (nonatomic, strong) UILabel *aLabel;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aLabel = [[UILabel alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aLabel.layer.borderColor = [UIColor grayColor].CGColor;
    self.aLabel.layer.borderWidth = 1;
    [self.view addSubview:self.aLabel];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"push到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

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

    B_ViewController *bViewController = [[B_ViewController alloc] init];
    //设置代理
    bViewController.delegate = self;
    [self.navigationController pushViewController:bViewController animated:YES];
}

/**
 什么时候可以用 代理 传值

 B 传到 A，反向传值

 B 在 A页面 初始化

 设置A为B的代理

 执行代理方法

 **/
- (void)transferString:(NSString *)string {

    self.aLabel.text = string;
}

@end

B控制器.h文件：

#import <UIKit/UIKit.h>

// 声明代理
@protocol BToADelegate <NSObject>

// 代理方法
- (void)transferString:(NSString *)string;

@end

@interface B_ViewController : UIViewController

// 代理属性
@property (nonatomic, weak) id<BToADelegate> delegate;

@end

B控制器.m文件：

#import "B_ViewController.h"

@interface B_ViewController ()

@property (nonatomic, strong) UITextField *bTextField;;

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    self.view.backgroundColor = [UIColor whiteColor];
    self.bTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.bTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.bTextField.layer.borderWidth = 1;
    [self.view addSubview:self.bTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传值A" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

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

    // 判断有没有代理以及代理是否响应代理方法
    if (self.delegate && [self.delegate respondsToSelector:@selector(transferString:)]) {
        [self.delegate transferString:self.bTextField.text];
    }

    [self.navigationController popToRootViewControllerAnimated:YES];
}

@end

Block传值
用法：反向传值：
需求：A-push到B，当B消失的时候，A中有一个Label需要显示从B中的一个TextField输入的内容，这时我们需要用到反向传值。

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"

@interface A_ViewController ()

@property (nonatomic ,strong) UILabel *aLabel;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aLabel = [[UILabel alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aLabel.layer.borderColor = [UIColor grayColor].CGColor;
    self.aLabel.layer.borderWidth = 1;
    [self.view addSubview:self.aLabel];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"push到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

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

    B_ViewController *bViewController = [[B_ViewController alloc] init];

    __weak __typeof(self) weakSelf = self;
    // block 回调接收
    [bViewController setBlock:^(NSString *string){
        weakSelf.aLabel.text = string;
    }];

    [self.navigationController pushViewController:bViewController animated:YES];
}

B控制器.h文件：

#import <UIKit/UIKit.h>

// 定义一个block
typedef void(^BToAblock)(NSString *string);

@interface B_ViewController : UIViewController

// block 属性
@property (nonatomic, copy)BToAblock block;

@end

B控制器.m文件：

#import "B_ViewController.h"

@interface B_ViewController ()

@property (nonatomic, strong) UITextField *bTextField;

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    self.view.backgroundColor = [UIColor whiteColor];
    self.bTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.bTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.bTextField.layer.borderWidth = 1;
    [self.view addSubview:self.bTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传值A" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

- (void)buttonAction:(UIButton *)sender {
    /**
     Blcok 传值

     反向传值

     B 传到 A
     */
    _block(self.bTextField.text);
    [self.navigationController popToRootViewControllerAnimated:YES];
}

@end

KVO传值
用法：反向传值：
需求：A-push到B，当B消失的时候，A中有一个Label需要显示从B中的一个TextField输入的内容，这时我们需要用到反向传值。

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"

@interface A_ViewController ()

@property (nonatomic, strong) UILabel *aLabel;
@property (nonatomic, strong) B_ViewController *bViewController;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aLabel = [[UILabel alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aLabel.layer.borderColor = [UIColor grayColor].CGColor;
    self.aLabel.layer.borderWidth = 1;
    [self.view addSubview:self.aLabel];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"push到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

    /**
     KVO 创建 三步一定要写
        1. 注册观察者
        2. KVO的回调
        3. 移除观察者

     */

    // B 传到 A ，反向传值
    //注册观察者，注意：观察者的注册和移除要对应，如果移除时发现没有注册观察者，程序会crash
     self.bViewController = [[B_ViewController alloc] init];
    [self.bViewController addObserver:self forKeyPath:@"string" options:NSKeyValueObservingOptionNew context:nil];
}

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

    [self.navigationController pushViewController:self.bViewController animated:YES];

}

// KVO的回调
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {

    if ([keyPath isEqualToString:@"string"]) {
        self.aLabel.text = self.bViewController.string;
    }

}
// KVO 的移除方式  （和通知一样要移除）
- (void)dealloc {

    [self.bViewController removeObserver:self forKeyPath:@"string"];
}

@end

B控制器.h文件：

#import <UIKit/UIKit.h>

@interface B_ViewController : UIViewController

@property (nonatomic, copy) NSString *string;

@end

B控制器.m文件：

#import "B_ViewController.h"

@interface B_ViewController ()

@property (nonatomic, strong) UITextField *bTextField;

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    self.view.backgroundColor = [UIColor whiteColor];
    self.bTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.bTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.bTextField.layer.borderWidth = 1;
    [self.view addSubview:self.bTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传值A" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

- (void)buttonAction:(UIButton *)sender {
    // KVO
    // 把self.bTextfield.text 赋值给当前属性
    // 在A中 监听 当前属性
    self.string = self.bTextField.text;

    [self.navigationController popToRootViewControllerAnimated:YES];
}

@end

通知传值
用法：正向传值
需求：当A-push到B时，B中有一个Label需要显示从A中的一个TextField输入的内容，这时我们需要用到正向传值。

用法：反向传值：
需求：A-push到B，当B消失的时候，A中有一个Label需要显示从B中的一个TextField输入的内容，这时我们需要用到反向传值。

我们在此将两种传值情况写到一个Demo中，所以将上述Label换为Textfield即可，如下：

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"

@interface A_ViewController ()

@property (nonatomic, strong) UITextField *aTextField;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.aTextField.layer.borderWidth = 1;
    [self.view addSubview:self.aTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

    // 接收通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(tzAction:) name:@"B2A" object:nil];
}

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

    // 通知传值 一般是用于回传

    // 现在是 A传到B，正向传值

    // 发送通知的方法 要写在执行方法里面

    B_ViewController *bViewController = [[B_ViewController alloc] init];

    [[NSNotificationCenter defaultCenter] postNotificationName:@"A2B" object:nil userInfo:@{@"key":self.aTextField.text}];

    [self.navigationController pushViewController:bViewController animated:YES];

}

// 回调通知
- (void)tzAction:(NSNotification *)sender {

    self.aTextField.text = sender.userInfo[@"key"];
}

// 移除通知
- (void)dealloc {

    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

@end

B控制器.m文件：

#import "B_ViewController.h"

@interface B_ViewController ()

@property (nonatomic, strong) UITextField *bTextField;

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传值A" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

//如果是从A传到B的话,B.m里要创建一个init方法,在里面写监听并在里面创建接收容器才能成功(因为程序先执行init方法再到viewDidLoad方法,当传值过去时在init就开始监听,如果这里没有创建textField接收,那就传不过去了,所以要在init里同时创建接收器(生命周期的问题));
-(instancetype)init
{
    if (self = [super init]) {

        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(tzAction:) name:@"A2B" object:nil];

        self.bTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

        self.bTextField.layer.borderColor = [UIColor grayColor].CGColor;
        self.bTextField.layer.borderWidth = 1;
        [self.view addSubview:self.bTextField];

    }

    return self;
}

//接收通知
- (void)tzAction:(NSNotification *)sender {

    self.bTextField.text = sender.userInfo[@"key"];

}

// 移除通知
- (void)dealloc  {

    // 移除所有
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    // 移除某个
    // [[NSNotificationCenter defaultCenter] removeObserver:self name:@"tz" object:nil];
}

//发送通知
- (void)buttonAction:(UIButton *)sender {
    // B传到A，反向传值
    [[NSNotificationCenter defaultCenter] postNotificationName:@"B2A" object:nil userInfo:@{@"key":self.bTextField.text}];

    [self.navigationController popToRootViewControllerAnimated:YES];

}

@end

单例传值
用法：正向传值
需求：当A-push到B时，B中有一个Label需要显示从A中的一个TextField输入的内容，这时我们需要用到正向传值。

用法：反向传值：
需求：A-push到B，当B消失的时候，A中有一个Label需要显示从B中的一个TextField输入的内容，这时我们需要用到反向传值。

我们在此将两种传值情况写到一个Demo中，所以将上述Label换为Textfield即可，如下：

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"
#import "DanLi.h"

@interface A_ViewController ()

@property (nonatomic, strong) UITextField *aTextField;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.aTextField.layer.borderWidth = 1;
    [self.view addSubview:self.aTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

}

- (void)viewWillAppear:(BOOL)animated
{
    // 单例 传值 B传到A （可以双向传值）
    DanLi *danli = [[DanLi alloc] init];

    self.aTextField.text = danli.value;
}

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

    // 单例 传值 A传到B （可以双向传值）
    DanLi *danli = [DanLi sharedDanLi];
    danli.value = self.aTextField.text;

    B_ViewController *bViewController = [[B_ViewController alloc] init];

    [self.navigationController pushViewController:bViewController animated:YES];

}

B控制器.m文件：

#import "B_ViewController.h"
#import "DanLi.h"

@interface B_ViewController ()

@property (nonatomic, strong) UITextField *bTextField;

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    self.view.backgroundColor = [UIColor whiteColor];
    self.bTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.bTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.bTextField.layer.borderWidth = 1;
    [self.view addSubview:self.bTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传值A" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

    self.bTextField.text = [DanLi sharedDanLi].value;
}

- (void)buttonAction:(UIButton *)sender {
    //B传给A
    [DanLi sharedDanLi].value = self.bTextField.text;
    [self.navigationController popToRootViewControllerAnimated:YES];
}

@end

单例类.h文件：

#import <Foundation/Foundation.h>

@interface DanLi : NSObject

//创建一个单例//如果在单线程里可以用nonatomic,如果在多线程里一定要用atomic,保证是只有一个在调用,不然在多线程里面如果多个方法调用修改单例类里的属性时会冲突
@property (atomic, copy) NSString *value;

+ (DanLi *)sharedDanLi;

@end

单例类.m文件：

#import "DanLi.h"

static DanLi *danli = nil;

@implementation DanLi

//实现方法,判断是否为空,是就创建一个全局实例给它
+ (DanLi *)sharedDanLi {

    if (danli == nil) {
        danli = [[DanLi alloc] init];
    }
    return danli;
}

//避免alloc/new创建新的实例变量--->增加一个互斥锁
+ (id)allocWithZone:(struct _NSZone *)zone {

    @synchronized(self) {
        if (danli == nil) {
            danli = [super allocWithZone:zone];
        }
    }
    return danli;
}

//避免copy,需要实现NSCopying协议
- (id)copyWithZone:(NSZone *)zone {
    return self;
}

@end

KVC传值
用法：正向传值
需求：当A-push到B时，B中有一个Label需要显示从A中的一个TextField输入的内容，这时我们需要用到正向传值。

A控制器.m文件：

#import "A_ViewController.h"
#import "B_ViewController.h"

@interface A_ViewController ()

@property (nonatomic, strong) UITextField *aTextField;

@end

@implementation A_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.title = @"A";
    self.view.backgroundColor = [UIColor whiteColor];
    self.aTextField = [[UITextField alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    self.aTextField.layer.borderColor = [UIColor grayColor].CGColor;
    self.aTextField.layer.borderWidth = 1;
    [self.view addSubview:self.aTextField];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传到B" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

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

    B_ViewController *bViewController = [[B_ViewController alloc] init];

    /**
        KVC 传值：这里只能传A传到B （因为 B在A页面提前初始化）
        B 有个属性 string
        用B对象 给B属性赋值（回顾下OC中KVC赋值 就理解了）

        这里forkey 一定要和B 属性名字一致 （也可以用@"_string"）因为是属性
     */

    // 给B属性string  赋值
    [bViewController setValue:self.aTextField.text forKey:@"string"];

    [self.navigationController pushViewController:bViewController animated:YES];
}

@end

B控制器.h文件：

#import <UIKit/UIKit.h>

@interface B_ViewController : UIViewController

@property (nonatomic, copy) NSString *string;

@end

B控制器.m文件：

#import "B_ViewController.h"

@interface B_ViewController ()

@end

@implementation B_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"B";
    self.view.backgroundColor = [UIColor whiteColor];

    self.view.backgroundColor = [UIColor whiteColor];
    UILabel *bLabel = [[UILabel alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 200, 100, 30)];

    bLabel.layer.borderColor = [UIColor grayColor].CGColor;
    bLabel.layer.borderWidth = 1;
    [self.view addSubview:bLabel];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2-50, 280, 100, 30);
    [button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [button setTitle:@"传值A" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];

    // KVC 接收值
    bLabel.text = self.string;
}

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

    [self.navigationController popToRootViewControllerAnimated:YES];
}

@end

好了，到此已经基本上介绍完页面传值了，相信你对页面传值已经有一定理解了吧，快去实践吧！

Jinge'blog

iOS探索之路

ios页面传值：正向、反向