人类的号角

Gjallarhorn 库中的核心类型实现 IObservable<'a>，这将使实现看起来很熟悉（记住 FSharp.ViewModule 示例中的 EventStream 属性）。对我们的模型唯一真正的改变是更新函数的参数的顺序。此外，我们现在使用术语 Message 而不是 Event 。

namespace ScoreLogic.Model

type Score = { ScoreA: int ; ScoreB: int }    
type ScoreMessage = IncA | DecA | IncB | DecB | NewGame

// Module showing allowed operations
[<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
module Score =
    let zero = {ScoreA = 0; ScoreB = 0}
    let update msg score =
        match msg with
        | IncA -> {score with ScoreA = score.ScoreA + 1}
        | DecA -> {score with ScoreA = max (score.ScoreA - 1) 0}
        | IncB -> {score with ScoreB = score.ScoreB + 1}
        | DecB -> {score with ScoreB = max (score.ScoreB - 1) 0}
        | NewGame -> zero

为了使用 Gjallarhorn 构建 UI，我们创建了简单的函数，称为 Component，而不是使类支持数据绑定。在它们的构造函数中，第一个参数 source 的类型为 BindingSource（在 Gjallarhorn.Bindable 中定义），用于将模型映射到视图，将视图中的事件映射回消息。

namespace ScoreLogic.Model

open Gjallarhorn
open Gjallarhorn.Bindable

module Program =

    // Create binding for entire application.
    let scoreComponent source (model : ISignal<Score>) =
        // Bind the score to the view
        model |> Binding.toView source "Score"

        [
            // Create commands that turn into ScoreMessages
            source |> Binding.createMessage "NewGame" NewGame 
            source |> Binding.createMessage "IncA" IncA
            source |> Binding.createMessage "DecA" DecA
            source |> Binding.createMessage "IncB" IncB
            source |> Binding.createMessage "DecB" DecB
        ]

当前实现与 FSharp.ViewModule 版本的不同之处在于，两个命令尚未正确实现 CanExecute。还列出了应用程序的管道。

namespace ScoreLogic.Model

open Gjallarhorn
open Gjallarhorn.Bindable

module Program =

    // Create binding for entire application.
    let scoreComponent source (model : ISignal<Score>) =
        let aScored = Mutable.create false
        let bScored = Mutable.create false

        // Bind the score itself to the view
        model |> Binding.toView source "Score"

        // Subscribe to changes of the score
        model |> Signal.Subscription.create 
            (fun currentValue -> 
                aScored.Value <- currentValue.ScoreA > 0
                bScored.Value <- currentValue.ScoreB > 0) 
            |> ignore

        [
            // Create commands that turn into ScoreMessages
            source |> Binding.createMessage "NewGame" NewGame 
            source |> Binding.createMessage "IncA" IncA
            source |> Binding.createMessageChecked "DecA" aScored DecA
            source |> Binding.createMessage "IncB" IncB
            source |> Binding.createMessageChecked "DecB" bScored DecB
        ]

    let application = 
        // Create our score, wrapped in a mutable with an atomic update function
        let score = new AsyncMutable<_>(Score.zero)

        // Create our 3 functions for the application framework

        // Start with the function to create our model (as an ISignal<'a>)
        let createModel () : ISignal<_> = score :> _

        // Create a function that updates our state given a message
        // Note that we're just taking the message, passing it directly to our model's update function,
        // then using that to update our core "Mutable" type.
        let update (msg : ScoreMessage) : unit = Score.update msg |> score.Update |> ignore

        // An init function that occurs once everything's created, but before it starts
        let init () : unit = ()

        // Start our application
        Framework.application createModel init update scoreComponent

留下设置解耦视图，结合 MainWindow 类型和逻辑应用程序。

namespace ScoreBoard.Views

open System

open FsXaml
open ScoreLogic.Model

// Create our Window
type MainWindow = XAML<"MainWindow.xaml"> 

module Main =    
    [<STAThread>]
    [<EntryPoint>]
    let main _ =  
        // Run using the WPF wrappers around the basic application framework    
        Gjallarhorn.Wpf.Framework.runApplication System.Windows.Application MainWindow Program.application

这总结了核心概念，有关其他信息和更详细的示例，请参阅 Reed Copsey 的帖子 。该圣诞树项目凸显了几个这种方法的好处：

• 有效赎回我们从需要（手动）模式复制到视图模型的自定义集合，管理它们，并手动构建模型与结果反馈。
• 集合内的更新以透明的方式完成，同时保持纯模型。
• 逻辑和视图由两个不同的项目托管，强调关注点的分离。