干净的方式强制视图提前加载子视图 [英] Clean way to force view to load subviews early

问题描述

最近我写了一些代码，我试图引用 UIViewController上的插座我刚用 [storyboard instantiateViewControllerWithIdentifier]实例化并在呈现 ViewController 之前修改插座指向的子视图。它没有用，因为 ViewController 的视图还没有加载它的子视图，包括我的出口引用的那个，所以属性只给了我一个空指针。

Recently I wrote some code where I tried to refer to an outlet on a UIViewController I'd just instantiated with [storyboard instantiateViewControllerWithIdentifier] and modify the subview that the outlet pointed to before presenting the ViewController. It didn't work because the ViewController's view hadn't loaded its subviews yet, including the one that my outlet referred to, so the property just gave me a null pointer.

在调试器中追踪我的问题的原因（经过一番努力）之后，我用Google搜索并通过这一个，我可以使视图加载其子视图而不显示通过调用 myViewController.view getter。在那之后，我可以毫无问题地访问我的插座。

After (with some struggle) tracking down the cause of my issue in the debugger, I Googled around and learned, through answers like this one, that I can cause the view to load its subviews without being displayed by calling the myViewController.view getter. After that, I can access my outlet without any problems.

这是一个明显的黑客，但是，Xcode - 非常正确 - 不喜欢它，并愤怒地抗议此警告：

It's a clear hack, though, and Xcode - quite rightly - doesn't like it, and angrily protests with this warning:

未使用属性访问结果 - 不应将getter用于副作用

Property access result unused - getters should not be used for side effects

是否有非hacky替代方法来执行此操作，但不涉及滥用 .view getter？或者，是否存在这种情况的规范/惯用模式，包括动态添加处理程序以便在加载子视图时立即调用？

Is there a non-hacky alternative way to do this that doesn't involved abusing the .view getter? Alternatively, are there canonical/idiomatic patterns for this scenario involving something like dynamically adding a handler to be called as soon as the subviews are loaded?

或者是标准解决方案用 [myViewController view] 替换 myViewController.view 来关闭Xcode的警告，然后和黑客一起生活？

Or is the standard solution just to replace myViewController.view with [myViewController view] to shut up Xcode's warning, and then live with the hack?

推荐答案

在iOS 9或更高版本上，可以使用：

On iOS 9 or newer, one can use:

viewController.loadViewIfNeeded()

文档： https://developer.apple.com/reference/uikit/uiviewcontroller/1621446-loadviewifneeded

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