如何設置一個簡單的代理來在兩個視圖控制器之間進行通信？

Question

我有兩個UITableViewControllers並需要使用委託將值從子視圖控制器傳遞給父級。我知道代表是誰，只是想看一個簡單的例子。

謝謝

Answer 1

簡單的例子網站...

假設子視圖控制器具有UISlider，我們希望通過委託傳遞滑塊的值回父。

在子視圖控制器的頭文件，聲明委託類型及其方法：

ChildViewController.h

#import <UIKit/UIKit.h> 

// 1. Forward declaration of ChildViewControllerDelegate - this just declares 
// that a ChildViewControllerDelegate type exists so that we can use it 
// later. 
@protocol ChildViewControllerDelegate; 

// 2. Declaration of the view controller class, as usual 
@interface ChildViewController : UIViewController 

// Delegate properties should always be weak references 
// See http://stackoverflow.com/a/4796131/263871 for the rationale 
// (Tip: If you're not using ARC, use `assign` instead of `weak`) 
@property (nonatomic, weak) id<ChildViewControllerDelegate> delegate; 

// A simple IBAction method that I'll associate with a close button in 
// the UI. We'll call the delegate's childViewController:didChooseValue: 
// method inside this handler. 
- (IBAction)handleCloseButton:(id)sender; 

@end 

// 3. Definition of the delegate's interface 
@protocol ChildViewControllerDelegate <NSObject> 

- (void)childViewController:(ChildViewController*)viewController 
      didChooseValue:(CGFloat)value; 

@end 

在子視圖控制器的實現，調用委託方法的要求。

ChildViewController.m

#import "ChildViewController.h" 

@implementation ChildViewController 

- (void)handleCloseButton:(id)sender { 
    // Xcode will complain if we access a weak property more than 
    // once here, since it could in theory be nilled between accesses 
    // leading to unpredictable results. So we'll start by taking 
    // a local, strong reference to the delegate. 
    id<ChildViewControllerDelegate> strongDelegate = self.delegate; 

    // Our delegate method is optional, so we should 
    // check that the delegate implements it 
    if ([strongDelegate respondsToSelector:@selector(childViewController:didChooseValue:)]) { 
     [strongDelegate childViewController:self didChooseValue:self.slider.value]; 
    } 
} 

@end 

在父視圖控制器的頭文件中，聲明它實現了ChildViewControllerDelegate協議。

RootViewController.h

#import <UIKit/UIKit.h> 
#import "ChildViewController.h" 

@interface RootViewController : UITableViewController <ChildViewControllerDelegate> 

@end 

在父視圖控制器的實現，適當地實現委託方法。

RootViewController.m

#import "RootViewController.h" 

@implementation RootViewController 

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { 
    ChildViewController *detailViewController = [[ChildViewController alloc] init]; 
    // Assign self as the delegate for the child view controller 
    detailViewController.delegate = self; 
    [self.navigationController pushViewController:detailViewController animated:YES]; 
} 

// Implement the delegate methods for ChildViewControllerDelegate 
- (void)childViewController:(ChildViewController *)viewController didChooseValue:(CGFloat)value { 

    // Do something with value... 

    // ...then dismiss the child view controller 
    [self.navigationController popViewControllerAnimated:YES]; 
} 

@end 

希望這有助於！

Answer 2

您需要使用委託和協議。下面是一個例子http://iosdevelopertips.com/objective-c/the-basics-of-protocols-and-delegates.html

Answer 3

下面的代碼只是顯示委託概念的最基本的用法。您根據您的要求命名變量和類。

首先，你需要聲明一個協議：

我們稱之爲MyFirstControllerDelegate.h

@protocol MyFirstControllerDelegate 
- (void) FunctionOne: (MyDataOne*) dataOne; 
- (void) FunctionTwo: (MyDatatwo*) dataTwo; 
@end 

導入MyFirstControllerDelegate。^ h文件並確認您的FirstController與協議MyFirstControllerDelegate

#import "MyFirstControllerDelegate.h" 

@interface FirstController : UIViewController<MyFirstControllerDelegate> 
{ 

} 

@end 

在實現文件中，你需要實現協議的兩個功能：在

@implementation FirstController 


    - (void) FunctionOne: (MyDataOne*) dataOne 
     { 
      //Put your finction code here 
     } 
    - (void) FunctionTwo: (MyDatatwo*) dataTwo 
     { 
      //Put your finction code here 
     } 

    //Call below function from your code 
    -(void) CreateSecondController 
    { 
      SecondController *mySecondController = [SecondController alloc] initWithSomeData:.]; 
      //..... push second controller into navigation stack 
      mySecondController.delegate = self ; 
      [mySecondController release]; 
    } 

@end 

您SecondController：

@interface SecondController:<UIViewController> 
{ 
    id <MyFirstControllerDelegate> delegate; 
} 

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

@end 

在執行文件SecondController。

@implementation SecondController 

@synthesize delegate; 
//Call below two function on self. 
-(void) SendOneDataToFirstController 
{ 
    [delegate FunctionOne:myDataOne]; 
} 
-(void) SendSecondDataToFirstController 
{ 
    [delegate FunctionTwo:myDataSecond]; 
} 

@end 

Here是關於委託的維基文章。

Answer 4

以下解決方案是使用委託將數據從VC2發送到VC1的非常基本和簡單的方法。

PS：該溶液在的Xcode 9.X製成，夫特4

聲明的協議和創建的委託變種成ViewControllerB

import UIKit 

    //Declare the Protocol into your SecondVC 
    protocol DataDelegate { 
     func sendData(data : String) 
    } 

    class ViewControllerB : UIViewController { 

    //Declare the delegate property in your SecondVC 
     var delegate : DataDelegate? 
     var data : String = "Send data to ViewControllerA." 
     override func viewDidLoad() { 
      super.viewDidLoad() 
     } 

     @IBAction func btnSendDataPushed(_ sender: UIButton) { 
       // Call the delegate method from SecondVC 
       self.delegate?.sendData(data:self.data) 
       dismiss(animated: true, completion: nil) 
      } 
     } 

ViewControllerA確認協議，並希望通過代理方法接收數據sendData

import UIKit 
     // Conform the DataDelegate protocol in ViewControllerA 
     class ViewControllerA : UIViewController , DataDelegate { 
     @IBOutlet weak var dataLabel: UILabel! 

     override func viewDidLoad() { 
      super.viewDidLoad() 
     } 

     @IBAction func presentToChild(_ sender: UIButton) { 
      let childVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier:"ViewControllerB") as! ViewControllerB 
      //Registered delegate 
      childVC.delegate = self 
      self.present(childVC, animated: true, completion: nil) 
     } 

     // Implement the delegate method in ViewControllerA 
     func sendData(data : String) { 
      if data != "" { 
       self.dataLabel.text = data 
      } 
     } 
    }