CK's Notepad

FSharp 也要走 minimal API 風

發表於 分類於 Disqus：

Minimal API 推出後，很多人慢慢能接受這樣的風格了，而 F# 當然也要來一波，以下是簡單跟風過程

基本型

透過 VS2022 建立一個空專案，語言選擇 F#，就完成了

image-20220130135421055

image-20220130135458674

後面就下一步到整個專案建立起來，然後就會看到一個很乾淨的 program.fs 了

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open System
open Microsoft.AspNetCore.Builder
open Microsoft.Extensions.Hosting

[<EntryPoint>]
let main args =
    let builder = WebApplication.CreateBuilder(args)
    let app = builder.Build()

    app.MapGet("/", Func<string>(fun () -> "Hello World!")) |> ignore

    app.Run()

    0 // Exit code

將專案執行起來後就可以看 Hello World! 的顯示

image-20220130141201938

來點變化

新增一個 HOme.fs 的檔案，然後將 root request 的動作搬到新檔案中，然後多點變化

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// Home.fs
module Home

open System
open Microsoft.AspNetCore.Builder

let showTime = 
    let getCurrentTime () = DateTime.Now
    Func<DateTime>(getCurrentTime)

let registerRoutes (app: WebApplication) =
    app.MapGet("/", showTime) |> ignore
    app

而原本的 Program.fs 就可以改成這樣

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open System
open Microsoft.AspNetCore.Builder
open Microsoft.Extensions.Hosting

[<EntryPoint>]
let main args =
    let builder = WebApplication.CreateBuilder(args)
    let app = builder.Build()

	// Changing
    app
    |> Home.registerRoutes
    |> ignore
    
    app.Run()

    0 // Exit code

這樣是不是就乾淨很多了，在來多寫一個 add/get items 的小功能

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// Todo.fs
[<RequireQualifiedAccess>]
module Todo

open System
open Microsoft.AspNetCore.Builder

type Todo = 
    { id: int
      title: string
      isDone: bool}

let mutable private todos = []

type ITodoService = 
   abstract GetTodos: unit -> Todo seq

let TodoService = { new ITodoService with
                       member this.GetTodos(): seq<Todo> =
                         todos |> List.toSeq  }

let private getTodos = 
    Func<ITodoService, Todo seq>
        (fun (todos: ITodoService) -> todos.GetTodos())

let private addTodo =
    Func<Todo, bool>
        (fun todo -> 
            todos <- todo:: todos
            true)

let registerRoutes (app: WebApplication) =
    app.MapGet("/todos", getTodos) |> ignore
    app.MapPost("/todos", addTodo) |> ignore
    app

Program.fs

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open System
open Microsoft.AspNetCore.Builder
open Microsoft.Extensions.Hosting
open Microsoft.Extensions.DependencyInjection // 註冊 service 需要的 namespace

[<EntryPoint>]
let main args =
    let builder = WebApplication.CreateBuilder(args)
    // 註冊 service
    builder
        .Services
        .AddSingleton<Todo.ITodoService>(fun _ -> Todo.TodoService) |> ignore

    let app = builder.Build()
   
    app
    |> Home.registerRoutes
    |> Todo.registerRoutes
    |> ignore

    
    app.Run()

    0 // Exit code


測試

寫完後就可以用 postman 來測試一下

  1. Query Items

    image-20220130144502653

  2. Add Item

    image-20220130144622387

    新增成功後在查詢看有沒有存進去

    image-20220130144654827

小結

同樣的架構在 F# 有可以試用，這是個好消息，之後會再嘗試接上 mongo了，此篇文章的程式碼是參考 Github Repo，也會在平日的晚上找時間開 F# 讀書會，有興趣的可以 follow 一下