macOS Swift:如何将NSDocument变量绑定到自定义NSView变量 [英] macOS Swift: How to bind NSDocument variable to custom NSView variable

问题描述

我有一个带有一个变量的简单自定义 NSView :

I have a simple custom NSView with one variable:

class MyView: NSView {
  var color: NSColor!
}

在我的 NSDocument 中，我具有相同的变量.

In my NSDocument I have the same variable.

目前我正在使用一个 NSViewController，当变量改变时，它通过 NSObjectProtocol 从文档接收消息.这意味着我已经通过默认的 NotificationCenter 设置了通知.然后，控制器在我的视图中通过 IBOutlet 设置颜色.

Currently I am using a NSViewController that receives messages from the document via the NSObjectProtocol when the variable changes. Which means I've set up notifications over the default NotificationCenter. Then the controller sets the color in my view over an IBOutlet.

效果很好，但是留下了很多胶水代码.

That works quite well but leaves me with a lot of glue code.

我当时想我可以使用 NSObjectController 并将其绑定到文档中的颜色.然后将我的颜色从视图绑定到objectController.

I was thinking I could use a NSObjectController and bind it to the color in my document. And then bind my color from the view to the objectController.

可能是我出了些问题，因为我很难访问甚至在视图中找不到color变量.它不会显示在Interface Builder故事板中.

Probably I got something wrong because I am having a hard time to access or even find the color variable in the view. It doesn't show up in the Interface Builder Storyboard.

我想知道如何在我的视图中准备可绑定的变量?！

I wonder how to prepare the variable in my view to be bindable?!

推荐答案

由于KVC和KVO是在Objective-C运行时上构建的，并且由于Cocoa绑定是在KVC和KVO之上构建的，因此您想要使用Cocoa的任何属性与的绑定需要暴露于Objective-C.至少，这意味着在声明中添加 @objc :

Since KVC and KVO are built on the Objective-C runtime, and since Cocoa Bindings is built on top of KVC and KVO, any properties you want to use Cocoa Bindings with need to be exposed to Objective-C. At the bare minimum, that means adding @objc to the declaration:

@objc var color: NSColor!

但是，如果可以在运行时更改 color 属性，则还需要跳过另外一个障碍.您需要确保在调用属性的setter时将触发KVO通知.苹果公司(Apple)的KVO实现将使用Objective-C魔术来自动向设置器添加所需的通知，但是由于不能保证Swift属性访问会通过Objective-C运行时，因此您需要添加 dynamic 使其可靠运行的关键字:

However, if the color property can be changed at runtime, there's an additional hurdle you need to jump through; you need to make sure that the KVO notifications will fire whenever the property's setter is called. Apple's implementation of KVO will use Objective-C magic to automatically add the needed notifications to the setter, but since Swift property accesses aren't guaranteed to go through the Objective-C runtime, you need to add the dynamic keyword for this to work reliably:

@objc dynamic var color: NSColor!

如果 color 是一个依赖于其他内容的计算属性，请改为设置一个 keyPathsForValuesAffecting< Key> 静态属性(暴露给Objective-C)，让KVO知道的依赖项:

If color is a computed property that depends on something else, set up a keyPathsForValuesAffecting<Key> static property instead (exposed to Objective-C) to let KVO know of the dependency:

@objc dynamic var foo: NSColor!

@objc private static let keyPathsForValuesAffectingColor: Set<String> = [#keyPath(foo)]

@objc var color: NSColor! { return self.foo }

如果 foo 发生更改，这将导致触发 color 的通知.

This will cause the notifications for color to be fired if foo changes.

无论如何，一旦您的媒体资源符合KVC规范，您就应该能够从Interface Builder绑定东西.

Anyway, once your property is KVC-compliant, you should be able to bind things to it from Interface Builder.

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