F# Add Constructor to a Record?
- by akaphenom
Basically I want to have a single construct to deal with serializing to both JSON and formatted xml. Records workd nicley for serializing to/from json. However XmlSerializer requires a parameterless construtor. I don't really want to have to go through the exercise of building class objects for these constructs (principal only). I was hoping there could be some shortcut for getting a parameterless constructor onto a record (perhaps with a wioth statement or something). I can't get it to behave - has anybody in the community had any luck?
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)
