Json parsing F#

Question

r@".NETFramework\v4.0\Profile\Client\System.Runtime.Serialization.dll"

open System.Runtime.Serialization
open System.Runtime.Serialization.Json

[<DataContract>]
    type geo = {
        [<field: DataMember(Name = "type")>]
        t:string
        [<field: DataMember(Name = "coordinates")>]
        coordinates:string
        }


let decode (s:string)  = 
    let json = new DataContractJsonSerializer(typeof<geo>)
    let byteArray = Encoding.UTF8.GetBytes(s)
    let stream = new MemoryStream(byteArray)
    json.ReadObject(stream) :?> geo

let tw = {"type":"Point","coordinates":[-7.002648,110.449961]}

decode tw

This returns -> End element 'coordinates' from namespace '' expected. Found element 'item' from namespace ''

How can I define the DataMember coordinates so that it understands ?

Thanks a lot

Tuomas Hietanen · Accepted Answer · 2011-01-03 15:15:27Z

7

Reference System.Runtime.Serialization and System.Xml

(Interactive: #r "System.Runtime.Serialization" )

open System.IO
open System.Runtime.Serialization.Json
open System.Xml
open System.Text

/// Object to Json 
let internal json<'t> (myObj:'t) =   
        use ms = new MemoryStream() 
        (new DataContractJsonSerializer(typeof<'t>)).WriteObject(ms, myObj) 
        Encoding.Default.GetString(ms.ToArray()) 


/// Object from Json 
let internal unjson<'t> (jsonString:string)  : 't =  
        use ms = new MemoryStream(ASCIIEncoding.Default.GetBytes(jsonString)) 
        let obj = (new DataContractJsonSerializer(typeof<'t>)).ReadObject(ms) 
        obj :?> 't

edited Jan 3, 2011 at 15:15

answered Jan 3, 2011 at 14:59

Tuomas Hietanen

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Comments

desco · Accepted Answer · 2010-08-24 13:37:33Z

6

this works for me

#r "System.Runtime.Serialization"

open System.IO
open System.Text
open System.Runtime.Serialization
open System.Runtime.Serialization.Json

[<DataContract>]
    type geo = {
        [<field: DataMember(Name = "type")>]
        t:string
        [<field: DataMember(Name = "coordinates")>]
        coordinates:float[]
        }


let decode (s:string)  = 
    let json = new DataContractJsonSerializer(typeof<geo>)
    let byteArray = Encoding.UTF8.GetBytes(s)
    let stream = new MemoryStream(byteArray)
    json.ReadObject(stream) :?> geo

let tw = "{
    \"type\":\"Point\",
    \"coordinates\":[-7.002648,110.449961]
    }"

let v = decode tw // val v : geo = {t = "Point"; coordinates = [|-7.002648; 110.449961|];}

edited Aug 24, 2010 at 13:37

answered Aug 24, 2010 at 12:42

desco

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4 Comments

jlezard Over a year ago

thank you for your reply, but there are no \" in the string to decode, so i need to find a way to make it work without them (other that tw.Replace("[",@"\"[").Replace("]",@"]\""), thanks !

desco Over a year ago

[-7.002648,110.449961] is not string value but array of floats, if you fix geo definition so coordinates field is float[] - it should fix this issue. I've corrected my sample to demonstrate this

jlezard Over a year ago

@Ronald Wildenberg Accepted ! Thanks

BitTickler Over a year ago

Small side note regarding how to write the tw definition without acquiring eye cancer: Use """ around your string literal and you can remove all the `\` stuff and have plain old JSON.

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