F＃记录

记录类似于一个元组，但它包含命名字段。 例如，

type website = { title : string; url : string }

定义记录

一个记录被定义为使用type关键字类型，记录的字段被定义为一个分号分隔的列表。

语法定义一个记录 

type recordName = { [ fieldName : dataType ] + }

创建记录

您可以通过指定记录的字段创建一个记录。例如，让我们创建一个网站记录中名为“homepage”

let homepage = { Title = "TutorialsPoint"; Url = "www.w3cschool.cn" }

下面的实例将解释其中的概念 

例1

此程序定义一个名为website的记录类型。 然后它创建一些类型的website记录并打印记录。

(* defining a record type named website *)type website = { Title : string; Url : string }(* creating some records *)let homepage = { Title = "TutorialsPoint"; Url = "www.w3cschool.cn" }let cpage = { Title = "Learn C"; Url = "www.w3cschool.cn/c/index.htm" }let fsharppage = { Title = "Learn F#"; Url = "www.w3cschool.cn/fsharp/index.htm" }let csharppage = { Title = "Learn C#"; Url = "www.w3cschool.cn/csharp/index.htm" }(*printing records *)(printfn "Home Page: Title: %A URL: %A") homepage.Title homepage.Url(printfn "C Page: Title: %A URL: %A") cpage.Title cpage.Url(printfn "F# Page: Title: %A URL: %A") fsharppage.Title fsharppage.Url(printfn "C# Page: Title: %A URL: %A") csharppage.Title csharppage.Url

当你编译和执行程序，它产生以下输出 

Home Page: Title: "TutorialsPoint" URL: "www.w3cschool.cn"C Page: Title: "Learn C" URL: "www.w3cschool.cn/c/index.htm"F# Page: Title: "Learn F#" URL: "www.w3cschool.cn/fsharp/index.htm"C# Page: Title: "Learn C#" URL: "www.w3cschool.cn/csharp/index.htm"

例2

type student = { Name : string; ID : int; RegistrationText : string; IsRegistered : bool }let getStudent name id = { Name = name; ID = id; RegistrationText = null; IsRegistered = false }let registerStudent st = { st with RegistrationText = "Registered"; IsRegistered = true }let printStudent msg st = printfn "%s: %A" msg stlet main() = let preRegisteredStudent = getStudent "Zara" 10 let postRegisteredStudent = registerStudent preRegisteredStudent printStudent "Before Registration: " preRegisteredStudent printStudent "After Registration: " postRegisteredStudentmain()

当你编译和执行程序，它产生以下输出 

Before Registration: : {Name = "Zara"; ID = 10; RegistrationText = null; IsRegistered = false;}After Registration: : {Name = "Zara"; ID = 10; RegistrationText = "Registered"; IsRegistered = true;}