f# - 我怎样才能干掉这个 F# 代码？ (流畅的界面)

Question

所以这是我写过的最潮湿的代码。但它很有用，这很烦人。所有重复的原因是因为我想保持界面流畅。如果我扩充基类(在这种情况下恰好是 View)，它只会返回 View 的实例，这将阻止我做类似的事情

let label = theme.CreateLabel().WithMargin(new Thickness(5.0)).WithText("Hello")

因为 Label.Text View 没有实现属性基类。

所以这是我的流畅界面。做好准备。这很丑陋，而且重复。但它也有效，并且使用方便。

我是否错过了一种明显的干燥方法？

module ViewExtensions =
    let private withTwoWayBinding<'TElement, 'TProperty, 'TViewModel, 'TView when 'TView :> IViewFor<'TViewModel>>(viewModel: 'TViewModel, view: 'TView, viewModelProperty: Expr<'TViewModel -> 'TProperty>, viewProperty: Expr<'TView -> 'TProperty>) (element: 'TElement) = 
        view.Bind(viewModel, ExpressionConversion.toLinq viewModelProperty, ExpressionConversion.toLinq viewProperty) |> ignore
        element
    let private withHorizontalOptions<'TElement when 'TElement :> View> options (element: 'TElement) =
        element.HorizontalOptions <- options
        element
    let private withVerticalOptions<'TElement when 'TElement :> View> options (element: 'TElement) =
        element.VerticalOptions <- options
        element
    let private withAlignment<'TElement when 'TElement :> View> horizontalOptions verticalOptions (control: 'TElement) =
        control |> withHorizontalOptions horizontalOptions |> withVerticalOptions verticalOptions
    let private withMargin<'TElement when 'TElement :> View> margin (element: 'TElement) = 
        element.Margin <- margin
        element
    let private withActions<'TElement> (actions: ('TElement -> unit)[]) (element: 'TElement) = 
        for action in actions do action(element)
        element
    type Xamarin.Forms.Entry with 
        member this.WithHorizontalOptions(options) = withHorizontalOptions options this
        member this.WithVerticalOptions(options) = withHorizontalOptions options this
        member this.WithAlignment(horizontalOptions, verticalOptions) = withAlignment horizontalOptions verticalOptions this
        member this.WithTwoWayBinding(viewModel, view, viewModelProperty, viewProperty) = withTwoWayBinding(viewModel, view, viewModelProperty, viewProperty) this
        member this.WithMargin(margin) = withMargin margin this
        member this.With(actions) = withActions actions this
        member this.With(action: Entry -> unit) = this.With([|action|])
    type Xamarin.Forms.Grid with 
        member this.WithHorizontalOptions(options) = withHorizontalOptions options this
        member this.WithVerticalOptions(options) = withHorizontalOptions options this
        member this.WithAlignment(horizontalOptions, verticalOptions) = withAlignment horizontalOptions verticalOptions this
        member this.WithMargin(margin) = withMargin margin this
        member this.With(actions) = withActions actions this
        member this.With(action: Grid -> unit) = this.With([|action|])
    type Xamarin.Forms.StackLayout with 
        member this.WithHorizontalOptions(options) = withHorizontalOptions options this
        member this.WithVerticalOptions(options) = withHorizontalOptions options this
        member this.WithAlignment(horizontalOptions, verticalOptions) = withAlignment horizontalOptions verticalOptions this
        member this.WithMargin(margin) = withMargin margin this
        member this.With(actions) = withActions actions this
        member this.With(action: StackLayout -> unit) = this.With([|action|])
    type Xamarin.Forms.Button with 
        member this.WithHorizontalOptions(options) = withHorizontalOptions options this
        member this.WithVerticalOptions(options) = withHorizontalOptions options this
        member this.WithAlignment(horizontalOptions, verticalOptions) = withAlignment horizontalOptions verticalOptions this
        member this.WithMargin(margin) = withMargin margin this
        member this.WithText(text) = this.Text <- text; this
        member this.With(actions) = withActions actions this
        member this.With(action: Button -> unit) = this.With([|action|])
    type Xamarin.Forms.Switch with 
        member this.WithHorizontalOptions(options) = withHorizontalOptions options this
        member this.WithVerticalOptions(options) = withHorizontalOptions options this
        member this.WithAlignment(horizontalOptions, verticalOptions) = withAlignment horizontalOptions verticalOptions this
        member this.WithTwoWayBinding(viewModel, view, viewModelProperty, viewProperty) = withTwoWayBinding(viewModel, view, viewModelProperty, viewProperty) this
        member this.WithMargin(margin) = withMargin margin this
        member this.With(actions) = withActions actions this
        member this.With(action: Switch -> unit) = this.With([|action|])
    type Xamarin.Forms.Label with 
        member this.WithHorizontalOptions(options) = withHorizontalOptions options this
        member this.WithVerticalOptions(options) = withHorizontalOptions options this
        member this.WithAlignment(horizontalOptions, verticalOptions) = withAlignment horizontalOptions verticalOptions this
        member this.WithMargin(margin) = withMargin margin this
        member this.WithText(text) = this.Text <- text; this
        member this.With(actions) = withActions actions this
        member this.With(action: Label -> unit) = this.With([|action|])

更新

因此，感谢您的帮助，答案是肯定的，我遗漏了一些明显的东西。正如 TheQuickBrownFox 解释的那样，如果我将流利的界面更改为某种形式

let label = theme.CreateLabel() |> withMargin(new Thickness(5.0)) |> withContent("Hello")

那么您在上面看到的怪物可以全部替换为

module ViewExtensions =
    let withTwoWayBinding<'TElement, 'TProperty, 'TViewModel, 'TView when 'TView :> IViewFor<'TViewModel>>(viewModel: 'TViewModel, view: 'TView, viewModelProperty: Expr<'TViewModel -> 'TProperty>, viewProperty: Expr<'TView -> 'TProperty>) (element: 'TElement) = 
        view.Bind(viewModel, ExpressionConversion.toLinq viewModelProperty, ExpressionConversion.toLinq viewProperty) |> ignore
        element
    let withHorizontalOptions options (element: #View) = element.HorizontalOptions <- options; element
    let withVerticalOptions options (element: #View) = element.VerticalOptions <- options; element
    let withAlignment horizontalOptions verticalOptions element = element |> withHorizontalOptions horizontalOptions |> withVerticalOptions verticalOptions
    let withMargin margin (element: #View) = element.Margin <- margin; element
    let withCaption text (element: #Button) = element.Text <- text; element
    let withText text (element: #Entry) = element.Text <- text; element
    let withContent text (element: #Label) = element.Text <- text; element
    let withSetUpActions<'TElement> (actions: ('TElement -> unit)[]) (element: 'TElement) = (for action in actions do action(element)); element
    let withSetUpAction<'TElement> (action: 'TElement -> unit) = withSetUpActions([|action|])

这种代码删除确实非常令人愉快。

Answer 1

流畅接口(interface)的惯用 F# 方法就是使用管道转发运算符 |>

module ViewHelpers
    let withMargin margin element = ...
    let withText text element = ...

open ViewHelpers

let label = theme.CreateLabel() |> withMargin (new Thickness(5.0)) |> withText "Hello"

我认为你也可以使用 flexible types 来缩短你的函数签名。 :

let withMargin margin (element: #View) = ...