从Storyboard实例化ViewController时崩溃 [英] Crash when instantiating ViewController from Storyboard

问题描述

我的情节提要中只有一个视图，可以通过执行以下操作将其添加到当前视图中:

I have got a single view in my storyboard, which I add to my current view by doing the following :

MainViewController *mvc = [self.storyboard instantiateViewControllerWithIdentifier:@"MainController"];
             [self.view addSubview:mvc.view];

该视图出现了，但是出现后我所做的一切都会导致崩溃.我在做什么错了?

The view appears, but everything I do after it appears, leads to a crash. What am I doing wrong ?

这里是一个当机的例子:

Here is an example when it crashes:

-(IBAction)showUsername:(id)sender{

    [testLabel setText:@"username"];

}

所有内容也都连接在情节提要中，因此错误链接的连接不应引起问题.

Everything is hooked up in storyboard as well, so falsely linked connections should not cause the problem.

推荐答案

您实例化一个新的视图控制器:

You instantiate a new view controller:

MainViewController *mvc = [self.storyboard instantiateViewControllerWithIdentifier:@"MainController"];

但是您不保留它.您将视图层次结构添加到另一个视图后，便立即将其分层.

But you do not retain it. Your view hierarchy is, as soon you added it to another view.

[self.view addSubview:mvc.view];

因此，当单击按钮时，一条消息会发送给您 IBAction ，但是您的视图控制器已被释放.为了防止这种情况发生，请保留您的 mvc 变量，例如在属性中的某个位置.

So when a button is clicked, a message is sent to you IBAction, but your view controller has been released already. To prevent this from happening, retain your mvc variable, for example somewhere in a property.

@property(nonatomic, strong) MainViewController *controller;

self.controller = mvc;

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