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Object expression question
f#

I'd like to be able to create a new instance of a concrete type but tack on an implementation of an interface at the same time. The F# manual seems suggest that this is possible:

Objects created via object expressions can also support multiple interfaces.. The syntax is: 

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{ new  with 
     interface  with 
     ...
     interface  with  }

but frankly I'm struggering a bit with the syntax:

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#light

open System
open System.Windows
open System.Windows.Controls


type IValueGetter =
    abstract Value : obj with get, set

let test = { new WrapPanel() with 
                 interface IValueGetter with
                    member x.Value
                      with get() = "" :> obj
                      and set x = ()  }

This gives me a syntax error on the interface keyword.

Cheers,
Rob

.

Since you aren't overriding any class methods, you don't need the "with" after the "new, so you can just use this:

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#light

open System
open System.Windows
open System.Windows.Controls

type IValueGetter =
    abstract Value : obj with get, set
let test = { new WrapPanel() 
             interface IValueGetter with
                member x.Value
                  with get() = "" :> obj
                  and set x = ()  }

This is correctly spec'd in our internal working spec (which we'll be making available in due course)

Thanks

don

By on 3/5/2008 12:51 PM ()

Will this work in the next version?

By on 2/14/2009 12:25 PM ()

I also didn't knowed about that...
thx..

By on 3/5/2008 11:23 PM ()

I wasn't aware of this. What a powerful feature! The mind reels...

By on 3/5/2008 3:09 PM ()

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