代理---视图间数据的传递：标签显示输入的内容【多个视图中】

RootViewController.h

#import "ModalViewController.h"

@interface RootViewController : UIViewController<ModalViewDelegate>

RootViewController.m

@interface RootViewController ()

@end

@implementation RootViewController {

    ModalViewController *modalCtrl;
    
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor redColor];
    
    UILabel *textLabel = [[UILabel alloc] initWithFrame:CGRectMake(50, 100, 200, 20)];
    textLabel.tag = 100;
    textLabel.backgroundColor = [UIColor orangeColor];
    [self.view addSubview:textLabel];
    
    
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(50, 150, 100, 30);
    [button setTitle:@"打开" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    
    
    modalCtrl = [[ModalViewController alloc] init];
    //设置代理对象
    modalCtrl.delegate = self;
    
}

- (void)buttonAction
{
    [self presentViewController:modalCtrl animated:YES completion:NULL];
    
}

//实现协议方法
- (void)responseData:(NSString *)text {

    UILabel *label = (UILabel *)[self.view viewWithTag:100];
    
    label.text = text;
    
}

ModalViewController.h

//返回文本数据
- (void)responseData:(NSString *)text;

@end

@interface ModalViewController : UIViewController <UITextFieldDelegate>

@property(nonatomic, assign)id<ModalViewDelegate> delegate;

ModalViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor greenColor];
    
    UITextField *textFiled = [[UITextField alloc] initWithFrame:CGRectMake(50, 60, 160, 30)];
    textFiled.tag = 100;
    textFiled.delegate = self;
    textFiled.borderStyle = UITextBorderStyleRoundedRect;
    [self.view addSubview:textFiled];
    //显示键盘
    [textFiled becomeFirstResponder];
    
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(50, 150, 100, 30);
    [button setTitle:@"返回" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
    
}

//按钮点击事件
- (void)buttonAction
{
    [self dismissViewControllerAnimated:YES completion:NULL];
    
    UITextField *field = (UITextField *)[self.view viewWithTag:100];
    NSString *text = field.text;
    
    //推断代理是否实现了协议方法
    if ([self.delegate respondsToSelector:@selector(responseData:)]) {
        //调用协议方法
        [self.delegate responseData:text];
    }
    
}

//点击return调用的协议方法
- (BOOL)textFieldShouldReturn:(UITextField *)textField {

    //收起键盘
    [textField resignFirstResponder];
    
    return YES;
    
}