将 Swift 块转换为 Objective-C 块

Question

在 Swift 中，我创建了一个闭包方法（我认为）：

func firstMove(action: UIAlertAction!) {
        if action.title == "Yes" {
            currentPlayer = "X"
        } else {
            currentPlayer = "0"
        }

我传入这个 UIAlertAction 方法：

let optionToStartController = UIAlertController(title: "", message: "Do you want first move?", preferredStyle: .Alert)
            optionToStartController.addAction(UIAlertAction(title: "Yes", style: .Default, handler: firstMove))

如何将闭包和方法都转换为 Objective-C？

我已经尝试过：

- (void)firstMove:(UIAlertAction*)action
{
  if ([action.title isEqual: @"Yes"]) {
    _currentPlayer = 'X';
} else {
    _currentPlayer = 'O';
 }
}

并像这样传递它：

UIAlertController *optionToStartController = [UIAlertController alertControllerWithTitle:@"" message:@"Do you want first move?" preferredStyle:UIAlertControllerStyleAlert];
[optionToStartController addAction:[UIAlertAction actionWithTitle:@"Yes" style:UIAlertActionStyleDefault handler: firstMove]];

Answer 1

您可能正在寻找块，它在 Objective-C 中大致相当于闭包。我不太确定您要完成什么，但以下代码定义了块 firstMove 以及它是如何从方法 addAction 传递和调用的。

void(^firstMove)(int) = ^(int x){
    NSLog(@"print y: %d", x);
};

[self addAction:firstMove];

...

-(void)addAction:(void(^)(int))y{
    y(5);
}

Answer 2

您可以查看示例。它应该可以正常工作。

UIAlertController * alert=   [UIAlertController
                                 alertControllerWithTitle:@"Question"
                                 message:@"Do you want first move?"
                                 preferredStyle:UIAlertControllerStyleAlert];
    //First button
   UIAlertAction* ok = [UIAlertAction
                        actionWithTitle:@"YES"
                        style:UIAlertActionStyleDefault
                        handler:^(UIAlertAction * action)
                        {
//Actions if the user press this button
//Dismiss the alertController. It's preferred to be in all actions.
                            [alert dismissViewControllerAnimated:YES completion:nil];
_currentPlayer = @"X";

                        }];

//Second Button
   UIAlertAction* cancel = [UIAlertAction
                            actionWithTitle:@"NO"
                           style:UIAlertActionStyleDefault
                           handler:^(UIAlertAction * action)
                           {
//Actions if the user press this button
//Dismiss the alertController. It's preferred to be in all actions.
                               [alert dismissViewControllerAnimated:YES completion:nil];
_currentPlayer = @"O";

                           }];
    //Add the actions to the alertController
   [alert addAction:ok];
   [alert addAction:cancel];


//present the alertController on the device. If you are writing this in the viewController, you can use self.view, if you are in UIView, then just self
   [self.view presentViewController:alert animated:YES completion:nil];