视图间跳转完成数据回调的三种方法

从视图Master跳转到视图Data，在Data视图中准备好数据，然后从Data视图回到Master视图，这个时候要将Data视图准备好的数据回调到Master视图中，此时有三种方法去实现。

方法一：使用全局变量

将Master视图控制器设置为全局变量，直接在Data视图控制器中进行存取。

首先在程序委托AppDelegate.h中声明全局变量：

#import <UIKit/UIKit.h>
#import "Global_MasterViewController.h"
#import "Property_MasterViewController.h"
#import "Delegate_MasterViewController.h"

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@property (strong, nonatomic) UITabBarController *tbc;

@property (strong, nonatomic) Global_MasterViewController *g_mVC; // 定义全局变量

@end

然后是Global_MasterViewController类：

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 标题
    self.navigationItem.title = @"Global";
    
    // Modal按钮，点击后跳转到Data视图
    CGRect rect = CGRectMake(120.0, 230.0, 80.0, 40.0);
    self.modal_button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.modal_button.frame = rect;
    [self.modal_button setTitle:@"Modal" forState:UIControlStateNormal];
    [self.modal_button addTarget:self action:@selector(modalToDataView:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.modal_button];
    
    // data标签，用来显示data视图中输入的数据
    rect = CGRectMake(100.0, 300.0, 120.0, 40.0);
    self.data_label = [[UILabel alloc] initWithFrame:rect];
    self.data_label.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:self.data_label];
}

// 跳转到Data视图
-(void)modalToDataView:(id)sender
{
    Global_DataViewController *g_dVC = [[Global_DataViewController alloc] init];
    g_dVC.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    [self presentViewController:g_dVC animated:YES completion:nil];
}

该视图有一个modal按钮，点击后跳转到Data视图，Data视图有一个文本输入框。

该视图的data标签用于显示Data视图输入的数据。
接着是Global_DataViewController类：

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 文本输入框，用于输入数据
    self.tf = [[UITextField alloc] initWithFrame:CGRectMake(100.0, 200.0, 120.0, 100.0)];
    self.tf.placeholder = @"Input some text";
    [self.view addSubview:self.tf];
    
    // Dismiss按钮，dismiss当前视图
    self.dismiss_button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.dismiss_button.frame = CGRectMake(130.0, 320.0, 60.0, 40.0);
    [self.dismiss_button setTitle:@"Dismiss" forState:UIControlStateNormal];
    [self.dismiss_button addTarget:self action:@selector(modalBack:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.dismiss_button];
}

// 回到Master视图，并完成数据回调
-(void)modalBack:(id)sender
{
    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; // 通过appDelegate获取全局变量g_mVC
    appDelegate.g_mVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
    [self dismissViewControllerAnimated:YES completion:^{
        appDelegate.g_mVC.data_label.text = self.tf.text; // 设置g_mVC中标签显示的数据
    }];
}

方法二：使用数据成员

将Master视图控制器设定为Data视图控制器的成员变量，然后可以在Data视图控制器中进行存取。

首先设定Master视图控制器类为Data视图控制器类的成员变量：

@interface Property_DataViewController : UIViewController

@property (strong, nonatomic) UIButton *dismiss_button;

@property (strong, nonatomic) UITextField *tf;

@property (strong, nonatomic) Property_MasterViewController *p_mVC; // 设定Master视图控制器为Data视图控制器的成员变量

@end

接着是Property_MasterViewController类：

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 标题
    self.navigationItem.title = @"Property";
    
    // Modal按钮，点击后跳转到Data视图
    CGRect rect = CGRectMake(120.0, 230.0, 80.0, 40.0);
    self.modal_button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.modal_button.frame = rect;
    [self.modal_button setTitle:@"Modal" forState:UIControlStateNormal];
    [self.modal_button addTarget:self action:@selector(modalToDataView:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.modal_button];

    // data标签，用来显示data视图中输入的数据
    rect = CGRectMake(100.0, 300.0, 120.0, 40.0);
    self.data_label = [[UILabel alloc] initWithFrame:rect];
    self.data_label.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:self.data_label];
}

// 跳转到Data视图
-(void)modalToDataView:(id)sender
{
    Property_DataViewController *p_dVC = [[Property_DataViewController alloc] init];
    p_dVC.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    [self presentViewController:p_dVC animated:YES completion:^{
        p_dVC.p_mVC = self; // 设定Data视图的master成员变量为self
    }];
}
在跳转时必须要设定好Data视图控制器的master成员变量为self。
最后是Property_DataViewController类：
- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 文本输入框，用于输入数据
    self.tf = [[UITextField alloc] initWithFrame:CGRectMake(100.0, 200.0, 120.0, 100.0)];
    self.tf.placeholder = @"Input some text";
    [self.view addSubview:self.tf];
    
    // Dismiss按钮，dismiss当前视图
    self.dismiss_button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.dismiss_button.frame = CGRectMake(130.0, 320.0, 60.0, 40.0);
    [self.dismiss_button setTitle:@"Dismiss" forState:UIControlStateNormal];
    [self.dismiss_button addTarget:self action:@selector(modalBack:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.dismiss_button];
}
                                                                                                                                                          // 跳转到Data视图
-(void)modalBack:(id)sender{
self.p_mVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; 
[self dismissViewControllerAnimated:YES completion:^{ self.p_mVC.data_label.text = self.tf.text; // 设置self.p_mVC中标签显示的数据 }];}

方法三：使用委托
由于Master视图控制器要使用Data视图控制器中的数据，所以可以在Data视图控制器中声明一个委托，然后Master视图控制器通过实现委托中的方法直接从Data视图控制器中获取数据。
先看看Data视图中委托的声明部分：

// 声明数据回调委托
@protocol DataCallBackDelegate <NSObject>
-(void)willDismissModalView:(id)sender;
@end

@interface Delegate_DataViewController : UIViewController

@property (strong, nonatomic) UIButton *dismiss_button;

@property (strong, nonatomic) UITextField *tf;

@property (weak, nonatomic) id<DataCallBackDelegate> dataDelegate; // 声明数据回调委托作为该类的成员变量，必须设定为weak属性，否则会形成retain cycle

@end

然后是Delegate_MasterViewController的接口部分：

@interface Delegate_MasterViewController : UIViewController <DataCallBackDelegate> // confirm to DataCallBackDelegate

@property (strong, nonatomic) UIButton *modal_button;

@property (strong, nonatomic) UILabel  *data_label;

@end

实现部分：

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 标题
    self.navigationItem.title = @"Delegate";
    
    // Modal按钮，点击后跳转到Data视图
    CGRect rect = CGRectMake(120.0, 230.0, 80.0, 40.0);
    self.modal_button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.modal_button.frame = rect;
    [self.modal_button setTitle:@"Modal" forState:UIControlStateNormal];
    [self.modal_button addTarget:self action:@selector(modalToDataView:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.modal_button];
    
    // data标签，用来显示data视图中输入的数据
    rect = CGRectMake(100.0, 300.0, 120.0, 40.0);
    self.data_label = [[UILabel alloc] initWithFrame:rect];
    self.data_label.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:self.data_label];
}

// 跳转到Data视图
-(void)modalToDataView:(id)sender
{
    Delegate_DataViewController *d_dVC = [[Delegate_DataViewController alloc] init];
    d_dVC.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
    d_dVC.dataDelegate = self; // 必须设定Data视图控制器的委托为self
    [self presentViewController:d_dVC animated:YES completion:nil];
}

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

#pragma mark -
#pragma mark Data call back delegate

// 实现委托中的方法
-(void)willDismissModalView:(id)sender
{
    Delegate_DataViewController *d_dVC = (Delegate_DataViewController *)sender;
    self.data_label.text = d_dVC.tf.text; // 设置self的标签显示的数据
}

最后看看Delegate_DataViewController类：

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 文本输入框，用于输入数据
    self.tf = [[UITextField alloc] initWithFrame:CGRectMake(100.0, 200.0, 120.0, 100.0)];
    self.tf.placeholder = @"Input some text";
    [self.view addSubview:self.tf];
    
    // Dismiss按钮，dismiss当前视图
    self.dismiss_button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.dismiss_button.frame = CGRectMake(130.0, 320.0, 60.0, 40.0);
    [self.dismiss_button setTitle:@"Dismiss" forState:UIControlStateNormal];
    [self.dismiss_button addTarget:self action:@selector(modalBack:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.dismiss_button];
}

// 回到Master视图，并完成数据回调
-(void)modalBack:(id)sender
{
    [self dismissViewControllerAnimated:YES completion:^{
        [self.dataDelegate willDismissModalView:self]; // 调用委托中的方法实现数据回调
    }];
}

这个比较特别：将委托的调用和实现分离开来。
在本例中，在Data视图控制器中调用委托方法：

// 回到Master视图，并完成数据回调
-(void)modalBack:(id)sender
{
    [self dismissViewControllerAnimated:YES completion:^{
        [self.dataDelegate willDismissModalView:self]; // 调用委托中的方法实现数据回调
    }];
}

实现则在Master视图控制器中完成：

// 实现委托中的方法
-(void)willDismissModalView:(id)sender
{
    Delegate_DataViewController *d_dVC = (Delegate_DataViewController *)sender;
    self.data_label.text = d_dVC.tf.text; // 设置self的标签显示的数据
}

注意要设置好委托为self。

Demo已上传，可以下载看看。