Swift协议不会触发Objective C协议方法

debugcn 发表于 Dev

Vee

我有一个Swift视图控制器，它定义了一个Objective-C视图控制器应该遵循的协议：

ChildViewController.swift

@objc public protocol ChildViewControllerDelegate {
    func closeChild();
}

@objc public class ChildViewController: UIViewController{

    var delegate: ChildViewControllerDelegate?

    @IBAction func childCloseButton(sender: UIButton) {
       delegate?.closeChild()
    }

}

MainViewController.m

@interface MainViewController () <ChildViewControllerDelegate>

@end

@implementation MainViewController
- (void)viewDidAppear:(BOOL)animated {
    // creating frame for child and placing it on the bottom of the screen
        CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width;
        CGFloat screenHeight = [UIScreen mainScreen].bounds.size.height;
        CGFloat yOffset = self.view.frame.origin.y;
        CGFloat childHeight = (8/15) * screenWidth;
        CGRect child = CGRectMake(0, screenHeight - yOffset - childHeight, screenWidth, childHeight);

        // adding storyboard 
        UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"child" bundle:nil];
        ChildViewController *childVC = [storyboard instantiateViewControllerWithIdentifier:@"childViewController"];
        childVC.view.frame = childBox;
        [self addChildViewController: childVC];
        [self.view addSubview:childVC.view];
}

- (void) closeChild {
    NSLog(@"Why doesn't this get trigger???");
}

@end

当我单击UI上的“ childCloseButton”时，MainViewController.m中的“ closeChild”方法似乎没有被调用。单步调试器，我发现“ delegate”属性ChildViewController.swift设置为nil，但我不明白为什么。有人可以告诉我我所缺少的吗？

西蒙·麦克劳林

ChildViewController正文中的第一行正在创建一个可选属性。直到设置了某些东西，这才是零。这里与委托没有什么独特的关系，这仅仅是面向对象的编程。

以相同的方式设置childVC稍后的frame属性MainViewController，您还需要将委托设置为的实例MainViewController。

例如

ChildViewController *childVC = [storyboard instantiateViewControllerWithIdentifier:@"childViewController"];
childVC.view.frame = childBox;
childVC.delegate = self

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