CODEWITHSUNDEEP
f#json.net
jackmott
jackmott

Reputation: 1172

Newtonsoft.Json DefaultSettings issue with F#

Newtonsoft's Json library has the ability to set global settings to apply custom converters and other settings. I've got a custom converter that works as long as I call it explicitly for each object I serialize, but I would like to set it globally so I don't have to do that. This can be done as shown here in C#:

https://stackoverflow.com/a/19121653/2506634

And the official signature of the DefaultSettings property is:

public static Func<JsonSerializerSettings> DefaultSettings { get; set; }

I've tried to translate this to F# like so:

JsonConvert.DefaultSettings = 
  System.Func<JsonSerializerSettings>
  (fun () ->           
    let settings = new JsonSerializerSettings()
    settings.Formatting <- Formatting.Indented
    settings.Converters.Add(new DuConverter())
    settings       
  )
  |> ignore

This compiles, and executes without error, but the custom converter is not applied when serializing. Also, for some reason setting the property returns a boolean (hence the |> ignore ) and I've noted that this boolean is false.

So, is something wrong with my translation to F#? Or is Newtonsoft perhaps ignoring my custom converter because the built in converter is being applied with precedence?

Upvotes: 2

Views: 608

Answers (1)

kvb
kvb

Reputation: 55184

As I said in the comments, you want to use the assignment operator (<-) instead of the equality operator (=). Note that once you do this, the compiler will also apply the delegate conversion for you automatically (and there's no result to ignore), so your code can just become:

JsonConvert.DefaultSettings <-
    fun () -> 
        let settings = new JsonSerializerSettings()
        settings.Formatting <- Formatting.Indented
        settings.Converters.Add(new DuConverter())
        settings

Upvotes: 3

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