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我正在重新设计一个库，我对当前的设计模式不满意。这个问题涉及将策略模式与State monad结合使用

我有一个Filter. 在其基本实现中，它所做的只是获取一些类型的数据馈送'd并更新自身，生成自身的新更新副本。

[<AbstractClass>]
type Filter<'d, 'F> (state: 'F) =
    member val StateVariable = state with get
    abstract member Update: 'd -> Filter<'d, 'F>

然后我有一个ISignalGenerator，它需要一个过滤器、环境数据并对其进行处理以生成一个Signal类型'S。

type ISignalGenerator<'d, 'F, 'S> =
    abstract member GenerateSignal: 'd -> Filter<'d,'F> -> 'S

是SignalGenerator一个策略模式对象。在SignalGenerator的实现中，库用户挂载将使用和组合以生成Signal.

我可以将我的代码包装在一个状态 monad中。与一些环境变量（数据馈送）一起，状态单子将携带“过滤器”作为状态。SignalGenerator然后将通过 state monad（类型的数据馈送'd和Filter） 获取状态更新

我的设计问题是我想将SignalGenerator类型与工作流的开发分离，即我想避免将 state monad 嵌套在SignalGenerator. 是否有功能设计模式来实现这一目标？

编辑

根据 Tomas 的评论，我制作了一个玩具模型。选择策略类是基于将许多函数包装在一起的需要。

/////////////////////////////////////////////////////////////////////////////////////
// Definition of the state 
/////////////////////////////////////////////////////////////////////////////////////
type StateFunc<'State, 'T> = 'State -> 'T * 'State
/////////////////////////////////////////////////////////////////////////////////////
// Definition of the State monad type
/////////////////////////////////////////////////////////////////////////////////////
type StateMonadBuilder<'State>() =

    // M<'T> -> M<'T>
    member b.ReturnFrom a : StateFunc<'State, 'T> = a

    // 'T -> M<'T>
    member b.Return a : StateFunc<'State, 'T> = ( fun s ->  a, s)

    // M<'T> * ('T -> M<'U>) -> M<'U>
    member b.Bind(p : StateFunc<_, 'T>, rest : 'T -> StateFunc<_,_>) : StateFunc<'State, 'U>  = 
        (fun s ->
            let a, s' = p s
            rest a s')

    // Getter for the whole state, this type signature is because it passes along the state & returns the state
    member b.getState : StateFunc<'State, _> = (fun s -> s, s)

    // Setter for the state
    member b.putState (s:'State) : StateFunc<'State, _> = (fun _ -> (), s)

/////////////////////////////////////////////////////////////////////////////////////
// The actual example
/////////////////////////////////////////////////////////////////////////////////////

let state = StateMonadBuilder<int> ()

// DoubleFunctOne defines standard operations that remain always the same
type Strategy (functOne) =
    member this.DoubleFunctOne (x: int) = state {
        let! res = functOne x
        return res * 2 }

// I introduce customization with the definition of this function.
// Whenever I need, I will swap the function with some other   
let myFunctOne x = state {        
    let someOtherFun x = x + 10 
    let! currState = state.getState
    return currState * someOtherFun x}

// Here I mount the custom function on the strategy class, so the Strategy.DoubleFunctOne can produce a result
// In order to do so, I need to keep the construction in the state monad 
let strategy1 = state {
    return Strategy (myFunctOne) }

// Here begins the client side. The client will consume the methods provided by my strategies.
// He should not be concerned by the construction of the strategies
// Ok, then, let's put our work in production
let test1 = (state {
    let! strategy = strategy1
    return! strategy.DoubleFunctOne 10 }) 9

我想知道是否会有一种模式解决方案，Strategy该类可以使用已安装的功能，而无需将状态单子嵌套在其腹部。换句话说，有没有办法推迟 的定义let state = StateMonadBuilder<int> ()，而不会陷入类型推断头痛？

我对函数式编程和 F# 比较陌生。请让我知道我的问题是否有意义！谢谢。

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0 回答 0