ios - 将数据从委托(delegate) View 发送到委托(delegate) View [Objective-C]

Question

所以我正在尝试学习如何将数据从一个 View Controller 发送到另一个 View Controller 。

到目前为止，我的代码获取从一个 VC (DelegateVC) 输入的数据，并将其显示在另一个 VC (ViewController) 的标签中。

这里的委托(delegate)是ViewController并且委托(delegate)是DelegateVC .

==================================================== ==========================

主要问题

但是如果我想从 ViewController 传递标签的数据怎么办？至DelegateVC ?我怎样才能做到这一点？我尝试设计相同的委托(delegate)概念，但使用 DelegateVC作为ViewController的委托(delegate).不确定这是否是写入方法。

TL;博士:

在 VC , 如果我点击 Next View , 我去 DelegateVC并输入“test”，它将显示在VC's receiving label作为“测试”。

现在下次我点击 Next View ，我希望现有标签的值显示在 TextField的 DelegateVC .而不是空白 TextField ，会有值“test”。

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假设我有一个 Main.storyboard像这样:


我有一个 ViewController.h文件为:

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController


@end

ViewController.m :

#import "ViewController.h"
#import "DelegatedVC.h"

@interface ViewController () <MainVCDelegate>
@property (strong, nonatomic) IBOutlet UILabel *receivingLabel;
- (IBAction)nextView:(id)sender;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}


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


- (IBAction)nextView:(id)sender {

}

-(void) sendBackData:(DelegatedVC *)delegatedVC :(NSString *)textField {
    [delegatedVC dismissViewControllerAnimated:YES completion:nil];
    self.receivingLabel.text = textField;
}
-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    DelegatedVC *secondVC = segue.destinationViewController;
    secondVC.delegate = self;
}
@end

DelegateVC.h:

#import <UIKit/UIKit.h>
@protocol MainVCDelegate;

@interface DelegatedVC : UIViewController
@property (strong, nonatomic) IBOutlet UITextField *sendDataTF;
- (IBAction)sendData:(id)sender;
@property (weak, nonatomic) id<MainVCDelegate> delegate;
@end

@protocol MainVCDelegate <NSObject>
-(void) sendBackData: (DelegatedVC *) delegatedVC : (NSString *) textField;
@end

DelegateVC.m:

#import "DelegatedVC.h"
@protocol MainVCDelegate;

@interface DelegatedVC ()

@end

@implementation DelegatedVC

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

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

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

- (IBAction)sendData:(id)sender {
    [self.delegate sendBackData: self : _sendDataTF.text];
}
@end

Answer 1

But what if I want to pass the data of the label from ViewController to DelegateVC? How can I accomplish this?

因此，正如我在您的代码中看到的那样，您正在正确地进行委派。回到你的主要问题，你只需要声明一个公共(public) NSString您的 DelegateVC.h 中的对象, 然后访问它并将数据从您的 ViewController 传递给的prepareForSegue .

下一步，在您的 DelegateVC.m 中，获取您的NSString对象的值并将其传递给您的 UITextField .

让我知道这是否有帮助:)