如何重载WPF容器的运算符？

Question

type AdderType() =
    /// Appends to the container.
    static member (+)
        (cont:DockPanel,child:#UIElement) =
        cont.Children.Add child |> ignore
        child

当我像上面那样上课并尝试这样的事情.

let dock = DockPanel()
let win = Window(Title = "Check the Window Style", Content = dock)
let menu = dock + Menu()

我得到的错误是None of the types 'DockPanel,Menu' support the operator '+'.我受到启发,由Phil Trelford的绑定示例制作上述内容,如下所示:

type DependencyPropertyValuePair(dp:DependencyProperty,value:obj) =
    member this.Property = dp
    member this.Value = value
    static member (+) 
        (target:#UIElement,pair:DependencyPropertyValuePair) =
        target.SetValue(pair.Property,pair.Value)
        target

以上由于某种原因起作用.我不知道为什么.是否有可能重载+或其他一些操作符,以便我可以优雅地添加控件到容器？

Answer 1

在类中定义的运算符仅在其中一个参数是类的实例时才起作用,但您可以将运算符定义为全局运算符:

let (++) (cont:DockPanel) (child:#UIElement) =
    cont.Children.Add child |> ignore
    child

然后应该有以下工作:

let dock = DockPanel()
let win = Window(Title = "Check the Window Style", Content = dock)
let menu = dock ++ Menu()

但说实话,我不认为这种问题是使用自定义运营商的好地方.+在这里使用是令人困惑的,因为你在任何意义上都没有真正添加两件事.您的运营商不是可交换的,例如(a ++ b) <> (b ++ a).

我认为一个更惯用的代码是定义一个命名函数并使用|>:

let appendTo (cont:DockPanel) (child:#UIElement) =
    cont.Children.Add child |> ignore
    child

let dock = DockPanel()
let win = Window(Title = "Check the Window Style", Content = dock)
let menu = Menu() |> appendTo dock