解包可选的 IBOutlet 值时为 Nil [英] Nil while unwrapping an Optional IBOutlet value

问题描述

我遇到了一个致命错误:在为 IBOutlet 解包可选值时意外发现 nil.

I have got a fatal error: unexpectedly found nil while unwrapping an Optional value for an IBOutlet.

在我的自定义视图中，我已将我的插座与 XIB 文件相关联.我已经仔细检查了这一点.这是它的样子:

In my custom view, I have associated my outlet with a XIB file. I have double checked this. This is how it looks like:

@IBOutlet weak var label: UILabel! {
    didSet {
        label.textColor = .redColor()
    }
}

我对 layoutSubviews 的实现如下:

override func layoutSubviews() {
    super.layoutSubviews()

    label.preferredMaxLayoutWidth = label.frame.size.width
}

尽管必须在 UI 元素初始化后调用 layoutSubviews 方法，但我收到一个错误:

Despite the fact, that layoutSubviews method has to be called after UI elements initialisation, I get an error:

fatal error: unexpectedly found nil while unwrapping an Optional value

此错误由行触发:

label.preferredMaxLayoutWidth = label.frame.size.width

为什么会这样?如何解决?

Why is that so? How to fix it?

推荐答案

尝试在 viewDidLayoutSubviews 而不是 layoutSubviews 中进行.您的 UI 元素应该在 viewDidLayoutSubviews 中准备好，但在 layoutSubviews 中不需要.

Try doing it in viewDidLayoutSubviews instead of layoutSubviews. You UI elements should be ready in viewDidLayoutSubviews, but not necessary in layoutSubviews.

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