如何在不传入值的情况下调用带参数的函数？ [斯威夫特游乐场]

Swift Playground provided the following code. How's the speakText(graphic: )called without passing in parameters? (Obviously graphic is already placed in another segment of the code)

Swift Playground提供了以下代码。如何在不传递参数的情况下调用speakText（graphic：）？（显然图形已经放在代码的另一部分）

// Speak the text of graphic.
func speakText(graphic: Graphic) {
    speak(graphic.text)
}
func addGreeting(touch: Touch) {
    if touch.previousPlaceDistance < 60 { return }
    let greetings = ["howdy!", "hello", "hi", "ciao", "yo!", "hey!",       "what’s up?"]
    let greeting = greetings.randomItem
    let graphic = Graphic(text: greeting)
    graphic.textColor = #colorLiteral(red: 0.9686274529, green: 0.78039217, blue: 0.3450980484, alpha: 1)
    graphic.fontName = .chalkduster
    scene.place(graphic, at: touch.position)
    graphic.rotation = randomDouble(from: -30, to: 30)
}
// Create and add Speak tool.
let speakTool = Tool(name: "Speak", emojiIcon: "????")
speakTool.onGraphicTouched = speakText(graphic: )
scene.tools.append(speakTool)

1 个解决方案

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speakTool is of type Tool which has a property onGraphicTouched that is of type (Graphic) -> () which is a function/closure that takes a Graphic as input and returns nothing (Void or ()).

speakTool是Tool类型，它有一个属性onGraphicTouched，类型为（Graphic） - >（），它是一个函数/闭包，它将一个Graphic作为输入并且不返回任何内容（Void或（））。

speakText(graphic:) is a function pointer to your function defined above. Note that that function has the required signature; it takes a Graphic and returns nothing.

speakText（graphic :)是指向上面定义的函数的函数指针。请注意，该函数具有所需的签名;它需要一个Graphic并且不返回任何内容。

So speakTool.onGraphicTouched = speakText(graphic: ) assigns a pointer to the function to onGraphicTouched and when the graphic is touched, the speakTool will call onGraphicTouched(someGraphic) which will call speakText(graphic: someGraphic).

所以speakTool.onGraphicTouched = speakText（graphic :)将指向函数的指针分配给onGraphicTouched，当触摸图形时，speakTool将调用onGraphicTouched（someGraphic），它将调用speakText（graphic：someGraphic）。

You can read more about this in the section on Function Types in Apple's Swift Guide.

您可以在Apple的Swift Guide中的“函数类型”一节中阅读更多相关内容。

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