如何清除这个F＃代码？ （流利的界面）

时间：2016-08-02 15:07:54

标签： f# xamarin.forms

所以这是我编写过的一些最潮湿的代码。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。如果我扩充了基类（在这种情况下恰好是View），它只会返回View的实例，这会阻止我做类似的事情

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

因为Label.Text基类没有实现View属性。

所以这是我流畅的界面。做好准备。它很难看，也很重复。但它也有效，并且使用方便。

我是否错过了明显的干涸方法？

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

感谢你的帮助，答案是肯定的，我错过了一些明显的东西。正如TheQuickBrownFox解释的那样，如果我将流畅的界面更改为某种形式

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

然后你可以通过

完全替换上面看到的怪物 
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|])

这段代码删除非常令人愉快。

1 个答案:

答案 0 :(得分：11)

流畅接口的惯用F＃方法只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"

我认为您还可以使用flexible types缩短功能签名：

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