F＃：有括號和不帶括號的類型之間的區別

Question

F＃中的type Something()和type Something有什麼區別？

爲什麼這個片段在ASP.NET Core 1.0 F# project作品引用：

open System 
open Microsoft.AspNetCore.Hosting 
open Microsoft.AspNetCore.Builder 
open Microsoft.AspNetCore.Hosting 
open Microsoft.AspNetCore.Http 

type Startup() = 
    member this.Configure(app: IApplicationBuilder) = 
     app.Run(fun context -> context.Response.WriteAsync("Hello from ASP.NET Core!")) 

[<EntryPoint>] 
let main argv = 
    let host = WebHostBuilder().UseKestrel().UseStartup<Startup>().Build() 
    host.Run() 
    printfn "Server finished!" 
    0 

但這種失敗：

open System 
open Microsoft.AspNetCore.Hosting 
open Microsoft.AspNetCore.Builder 
open Microsoft.AspNetCore.Hosting 
open Microsoft.AspNetCore.Http 

type Startup = 
    member this.Configure(app: IApplicationBuilder) = 
     app.Run(fun context -> context.Response.WriteAsync("Hello from ASP.NET Core!")) 

[<EntryPoint>] 
let main argv = 
    let host = WebHostBuilder().UseKestrel().UseStartup<Startup>().Build() 
    host.Run() 
    printfn "Server finished!" 
    0 

Answer 1

您可以通過在F＃互動鍵入它看到了差距：

type Parens() = 
    member this.add10 x = x + 10 

type NoParens = 
    member this.add10 x = x + 10;; 

輸出：

type Parens = 
    class 
    new : unit -> Parens 
    member add10 : x:int -> int 
    end 
type NoParens = 
    class 
    member add10 : x:int -> int 
    end 

第二個類沒有定義構造函數。編譯器不應該允許的東西，但出於某種原因。它不會生成像C＃這樣的自動構造函數。

欲瞭解更多信息，請查閱F＃以獲取更多樂趣和獲利關於classes和interfaces的網頁。另外看看這個StackOverflow post

並且爲了將來的參考，當有疑問的時候，打開F＃interactive，輸入你想查看的兩個東西之間的區別，並比較輸出結果。這是一個強大的工具，你應該使用它。