NSPopUpButton在Swift Playground中变灰

Question

在Swift playground视图控制器中，我有以下代码：

var jsonSelector = NSPopUpButton(title: "Path", target: self, action: #selector(updatePointFile))

override public func loadView() {
    let frame = CGRect(origin: CGPoint.zero, size: CGSize(width: 900, height: 600))
    let view = NSView(frame: frame)

    let array = // gets array of items
    for item in array {
        jsonSelector.addItem(withTitle: item)
    }

    view.addSubview(jsonSelector)
    self.view = view
}

@objc func updatePointFile() {
    let file = jsonSelector.selectedItem?.title ?? "swiftLogo"
    ...
}

它运行时最初看起来很正常：

但是一旦它被点击它看起来像：

当你点击它时它会保持不可点击：

当我将完全相同的代码复制到一个完整的Mac应用程序时，它就像正常一样工作，并且为了使事情变得更奇怪，有一次当我拍摄这些截图时，它一次性选择并返回到它的灰色状态。

任何帮助将不胜感激。

Answer 1

所以解决这个问题有点奇怪。它只需要稍后定义目标。

这意味着

var jsonSelector = NSPopUpButton(frame: NSRect(origin: CGPoint.zero, size: CGSize(width: 100, height: 50)))

override public func loadView() {
    jsonSelector.target = self
        jsonSelector.action = #selector(updatePointFile)

    let array = // gets array of items
    for item in array {
        jsonSelector.addItem(withTitle: item)
    }

    view.addSubview(jsonSelector)
    self.view = view
}

@objc func updatePointFile() {
    let file = jsonSelector.selectedItem?.title ?? "swiftLogo"
    ...
}

要么

var jsonSelector = NSPopUpButton(title: "Path", target: self, action: #selector(updatePointFile))

override public func loadView() {
    let frame = CGRect(origin: CGPoint.zero, size: CGSize(width: 900, height: 600))
    let view = NSView(frame: frame)

    jsonSelector.target = self

    let array = // gets array of items
    for item in array {
        jsonSelector.addItem(withTitle: item)
    }

    view.addSubview(jsonSelector)
    self.view = view
}

@objc func updatePointFile() {
    let file = jsonSelector.selectedItem?.title ?? "swiftLogo"
    ...
}

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