如何避免在 QML 初始化时创建属性绑定? [英] How can I avoid creating a property binding on initialization in QML?

问题描述

我想创建一个具有两个属性 one 和 two 的自定义 QML 组件，它们在未初始化时应该具有默认值.特别是，如果 two 应该得到一个依赖于 one 的初始值.以下代码

I want to create a custom QML component with two properties one and two, which should have default values when left uninitialized. In particular, if two should get an initial value depeding on one. The following code

Rectangle {
  property int one: 1
  property int two: 2 * one
}

然而会创建一个属性绑定:每当 one 更改时，two 都会更新为 2 * one 的新值.如何在不创建绑定的情况下将 two 初始化为 2 * one 的 value?

however creates a property binding: Whenever one changes, two is updated to the new value of 2 * one. How can I initialize two to the value of 2 * one without creating a binding?

推荐答案

一种明确告诉您不需要绑定的方法是在表达式块中调用赋值:

A way to explicitly tell that you don't want a binding is to call an assignment in an expression block:

Rectangle {
  property int one: 1
  property int two: {two = 2 * one}
}

与在onCompleted中打破绑定的方法不同，表达式块避免了绑定对象的创建和销毁，看起来更干净.

Unlike the approach of breaking the binding in onCompleted, the expression block avoids the creation and then destruction of a binding object, and it looks cleaner.

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