F＃将构造函数添加到记录中？

Question

基本上我想有一个单一的构造来处理序列化到JSON和格式化的XML。记录很适合序列化到/从JSON。但是XmlSerializer需要一个无参数的构造器。我并不想通过为这些结构构建类对象（仅适用于原理）。我希望可以有一些快捷方式让一个无参数的构造函数到一个记录上（也许有一个wioth语句或某个东西）。我无法做到这一点 - 社区中有没有人有幸运？

module JSONExample 
    open System 
    open System.IO 
    open System.Net 
    open System.Text 
    open System.Web 
    open System.Xml 
    open System.Security.Authentication 
    open System.Runtime.Serialization //add assemnbly reference System.Runtime.Serialization System.Xml 
    open System.Xml.Serialization 
    open System.Collections.Generic 

    [<DataContract>]    
    type ChemicalElementRecord = { 
     [<XmlAttribute("name")>] 
     [<field: DataMember(Name="name") >] 
     Name:string 

     [<XmlAttribute("name")>] 
     [<field: DataMember(Name="boiling_point") >] 
     BoilingPoint:string 

     [<XmlAttribute("atomic-mass")>] 
     [<field: DataMember(Name="atomic_mass") >] 
     AtomicMass:string 
    } 

    [<XmlRoot("freebase")>] 
    [<DataContract>] 
    type FreebaseResultRecord = { 
     [<XmlAttribute("code")>] 
     [<field: DataMember(Name="code") >] 
     Code:string 

     [<XmlArrayAttribute("results")>] 
     [<XmlArrayItem(typeof<ChemicalElementRecord>, ElementName = "chemical-element")>] 
     [<field: DataMember(Name="result") >] 
     Result: ChemicalElementRecord array 

     [<XmlElement("message")>] 
     [<field: DataMember(Name="message") >] 
     Message:string 
     } 


    let getJsonFromWeb() = 
     let query = "[{'type':'/chemistry/chemical_element','name':null,'boiling_point':null,'atomic_mass':null}]" 
     let query = query.Replace("'","\"") 
     let queryUrl = sprintf "http://api.freebase.com/api/service/mqlread?query=%s" "{\"query\":"+query+"}" 

     let request : HttpWebRequest = downcast WebRequest.Create(queryUrl) 
     request.Method <- "GET" 
     request.ContentType <- "application/x-www-form-urlencoded" 

     let response = request.GetResponse() 

     let result = 
      try 
       use reader = new StreamReader(response.GetResponseStream()) 
       reader.ReadToEnd(); 
      finally 
       response.Close() 

     let data = Encoding.Unicode.GetBytes(result); 
     let stream = new MemoryStream() 
     stream.Write(data, 0, data.Length); 
     stream.Position <- 0L 
     stream 



    let test = 
     // get some JSON from the web 
     let stream = getJsonFromWeb() 

     // convert the stream of JSON into an F# Record 
     let JsonSerializer = Json.DataContractJsonSerializer(typeof<FreebaseResultRecord>) 
     let result: FreebaseResultRecord = downcast JsonSerializer.ReadObject(stream) 

     // save the Records to disk as JSON 
     use fs = new FileStream(@"C:\temp\freebase.json", FileMode.Create) 
     JsonSerializer.WriteObject(fs,result) 
     fs.Close() 

     // save the Records to disk as System Controlled XML 
     let xmlSerializer = DataContractSerializer(typeof<FreebaseResultRecord>); 
     use fs = new FileStream(@"C:\temp\freebase.xml", FileMode.Create) 
     xmlSerializer.WriteObject(fs,result) 
     fs.Close() 

     use fs = new FileStream(@"C:\temp\freebase-pretty.xml", FileMode.Create) 
     let xmlSerializer = XmlSerializer(typeof<FreebaseResultRecord>) 
     xmlSerializer.Serialize(fs,result) 
     fs.Close() 

ignore(test) 

Answer 1

看起来你无法记录更改为一类 - 或添加edfault构造它。

提供的示例（基于此文章：http://blogs.msdn.com/b/jomo_fisher/archive/2010/03/06/neat-sample-f-and-freebase.aspx）从api.freebase.com获取json流;然后我们反序列化为属性类;接下来将其序列化为Json到磁盘;然后将它作为Xml序列化到磁盘（使用DataContract）;最后，与输出的最佳控制研究序列为XML到磁盘（使用XmlSerializer的）：

注：

DataContract（家庭）属性 DataContractJsonSerializer和 JSON.DataContractJsonSerializer - 这些发生超过班级名称和记忆变量。 DataContract 的东西很简单 - 也适用于记录类型。

XmlSerializer（系列）属性 类和属性 Getter/Setter。这要求类型 是具有默认 构造函数的对象，以及属性Getters和 具有与它们中的每个相关联的 属性的设置器。如果一个属性不 有eitehr一个getter或setter方法它 不会序列化 - 这是一个 惊喜（我想象中的默认 onstructor将确保 对象在 反序列化有defulat值和setter方法会 更新与任何序列化 - 但没有这不是这种情况）。

另一个漂亮（叹气）件事 XmlSerialization是，类 不能被包含在一个模块内。所以 我们移动种类多达命名空间...

namespace JSONExample 
    open System 
    open System.IO 
    open System.Net 
    open System.Text 
    open System.Web 
    open System.Xml 
    open System.Security.Authentication 
    open System.Runtime.Serialization //add assemnbly reference System.Runtime.Serialization System.Xml 
    open System.Xml.Serialization 
    open System.Collections.Generic 

    [<DataContract>]    
    type ChemicalElementRecord() = 
     [<field: DataMember(Name="name") >] 
     let mutable name: string = "" 

     [<field: DataMember(Name="boiling_point") >] 
     let mutable boilingPoint: string ="" 

     [<field: DataMember(Name="atomic_mass") >] 
     let mutable atomicMass: string = "" 

     [<XmlAttribute("name")>] 
     member this.Name with get() = name and set v = name <- v 

     [<XmlAttribute("boiling-point")>] 
     member this.BoilingPoint with get() = boilingPoint and set v = boilingPoint <- v 

     [<XmlAttribute("atomic-mass")>] 
     member this.AtomicMass with get() = atomicMass and set v = atomicMass <- v 

    [<XmlRoot("freebase")>] 
    [<DataContract>] 
    type FreebaseResultRecord() = 

     [<field: DataMember(Name="code") >] 
     let mutable code: string = "" 

     [<field: DataMember(Name="result") >] 
     let mutable result: ChemicalElementRecord array = Array.empty 

     [<field: DataMember(Name="message") >] 
     let mutable message: string = "" 

     [<XmlElement("message")>] 
     member this.Message with get() : string = message and set v = message <- v 

     [<XmlArrayAttribute("chemical-elements")>] 
     [<XmlArrayItem(typeof<ChemicalElementRecord>, ElementName = "chemical-element")>] 
     member this.Result with get() = result and set v = result <- v 

     [<XmlAttribute("code")>] 
     member this.Code with get() = code and set v = code <- v 

    module Test = 
     let getJsonFromWeb() = 
      let query = "[{'type':'/chemistry/chemical_element','name':null,'boiling_point':null,'atomic_mass':null}]" 
      let query = query.Replace("'","\"") 
      let queryUrl = sprintf "http://api.freebase.com/api/service/mqlread?query=%s" "{\"query\":"+query+"}" 

      let request : HttpWebRequest = downcast WebRequest.Create(queryUrl) 
      request.Method <- "GET" 
      request.ContentType <- "application/x-www-form-urlencoded" 

      let response = request.GetResponse() 

      let result = 
       try 
        use reader = new StreamReader(response.GetResponseStream()) 
        reader.ReadToEnd(); 
       finally 
        response.Close() 

      let data = Encoding.Unicode.GetBytes(result); 
      let stream = new MemoryStream() 
      stream.Write(data, 0, data.Length); 
      stream.Position <- 0L 
      stream 



     let test = 
      // get some JSON from the web 
      let stream = getJsonFromWeb() 

      // convert the stream of JSON into an F# Record 
      let JsonSerializer = Json.DataContractJsonSerializer(typeof<FreebaseResultRecord>) 
      let result: FreebaseResultRecord = downcast JsonSerializer.ReadObject(stream) 

      // save the Records to disk as JSON 
      use fs = new FileStream(@"C:\temp\freebase.json", FileMode.Create) 
      JsonSerializer.WriteObject(fs,result) 
      fs.Close() 

      // save the Records to disk as System Controlled XML 
      let xmlSerializer = DataContractSerializer(typeof<FreebaseResultRecord>); 
      use fs = new FileStream(@"C:\temp\freebase.xml", FileMode.Create) 
      xmlSerializer.WriteObject(fs,result) 
      fs.Close() 

      use fs = new FileStream(@"C:\temp\freebase-pretty.xml", FileMode.Create) 
      let xmlSerializer = XmlSerializer(typeof<FreebaseResultRecord>) 
      xmlSerializer.Serialize(fs,result) 
      fs.Close() 


     ignore(test) 

Answer 2

为什么不使用DataContractSerializer（用于Xml）而不是XmlSerializer？这是数据合同的主要优点之一（针对多个投影的相同编程模型）。

（有没有办法让一个F＃记录一个参数的构造函数）。

Answer 3

大段引用我希望有可能会有一些快捷方式获取参数的构造函数到记录

这是可能的在F＃版本3.0中通过使用CLIMutable属性。将它添加到无参数构造函数的记录类型和读/写属性（而不是只读属性）。