Elm 如何在测试API模块内的Cmd msg上进行模式匹配？

如何在测试API模块内的Cmd msg上进行模式匹配

我有一个测试API作为web服务的替代品

sources : Id -> (Result Http.Error (List Source) -> msg) -> Cmd msg
sources profileId msg =
    [ { platform = "WordPress", username = "bizmonger", linksFound = 0 }
    , { platform = "YouTube", username = "bizmonger", linksFound = 0 }
    , { platform = "StackOverflow", username = "scott-nimrod", linksFound = 0 }
    ]
        |> Result.Ok
        |> msg
        |> Task.succeed
        |> Task.perform identity

问题：

我收到以下代码的编译错误：

addSource : Id -> Source -> (Result Http.Error (List Source) -> msg) -> Cmd msg
addSource profileId source msg =
    let
        result =
            sources profileId msg
    in
        case result of
            Ok sources ->
                (source :: sources)
                    |> Result.Ok
                    |> msg
                    |> Task.succeed
                    |> Task.perform identity

            Err _ ->
                Cmd.none

Ok sources->^^^^^^^^^^^^模式与类型匹配：

Result error value

但它实际上要匹配的值是：

Cmd msg

注意：

type alias Source =
    { platform : String, username : String, linksFound : Int }

我知道这些函数返回Cmd-msg，我需要在Cmd-msg上进行模式匹配。但是，此代码位于TestAPI模块中，而不是典型的UI模块。因此，我认为我不必为依赖此TestAPI模块的UI客户端中已经定义的各种消息定义有区别的联合

附录：

type alias Source =
    { platform : String, username : String, linksFound : Int }

因为这是关于“模拟”API端点的，所以我将避免使用通常的“如果没有触发副作用，就不要在命令中装箱数据”spiel

相反，让我建议拆分

源

函数：

sourceData : List Source
sourceData =
    [ { platform = "WordPress", username = "bizmonger", linksFound = 0 }
    , { platform = "YouTube", username = "bizmonger", linksFound = 0 }
    , { platform = "StackOverflow", username = "scott-nimrod", linksFound = 0 }
    ]


mockResponse : a -> (Result Http.Error a -> msg) -> Cmd msg
mockResponse data tagger =
    Result.Ok data
        |> Task.succeed
        |> Task.perform tagger


sources : Id -> (Result Http.Error (List Source) -> msg) -> Cmd msg
sources profileId msg =
    mockResponse sourceData msg

现在，实现

addSource

函数变得相当简单，如下所示：

addSource : Id -> Source -> (Result Http.Error (List Source) -> msg) -> Cmd msg
addSource profileId source msg 
    mockResponse (source :: sourceData) msg

---

我意识到我还在做函数式编程。 因此，为什么不从核心要素到更复杂的功能组合在一起呢

因此，我做了以下工作：

addSourceBase : Id -> Source -> List Source
addSourceBase profileId source =
    source :: (profileId |> sourcesBase)


addSource : Id -> Source -> (Result Http.Error (List Source) -> msg) -> Cmd msg
addSource profileId source msg =
    source
        |> addSourceBase profileId
        |> Result.Ok
        |> msg
        |> Task.succeed
        |> Task.perform identity

---

赞成。。这就是我最后做的。