JS Function => CLR Delegate

[dahlbyk]

With IronPython, I can do this:

var script = @"
def inc(x):
    return x+1
";
var pythonEngine = Python.CreateEngine();
var scope = pythonEngine.CreateScope();
pythonEngine.Execute(script, scope);
var inc = (Func<int, int>)scope.GetVariable("inc");
var three = inc(2);

I'm trying to do something similar with IronJS:

var script = @"
function inc(x) {
    return x+1;
}
";
var context = new IronJS.Hosting.CSharp.Context();
context.Execute(script);
var inc = context.GetGlobalAs<Func<int, int>>("inc");
var three = inc(2);

However, I get the following exception:

System.InvalidCastException: Unable to cast object of type 'IronJS.FunctionObject' to type 'System.Func`2[System.Int32,System.Int32]'.
at Microsoft.FSharp.Core.LanguagePrimitives.IntrinsicFunctions.UnboxGeneric[T](Object source)
at IronJS.Hosting.CSharp.Context.GetGlobalAs[a](String name)

Is there a better way to export script as an executable delegate? Or if not, is this something you think IronJS could/should support? I'd be glad to help, but am unsure exactly where to start...maybe TypeConverter.ConvertTo()?

[fholm]

Yes there is a way to get a JS function as a CLR delegate, it's currently a bit clunky as it doesn't masqurade the internal parameters or return types and they get exposed to the hosting code, but here's the snippet:

var ctx = new IronJS.Hosting.CSharp.Context();

ctx.Execute(@"
    function multiply(a, b) {
        return a * b;
    }
");


var multiply = ctx.GetGlobalAs<FunctionObject>("multiply");
var delegate_ = multiply.MetaData.GetDelegate<Func<FunctionObject, CommonObject, double, double, BoxedValue>>(multiply);
var result = delegate_.Invoke(multiply, ctx.Globals, 4.0, 4.0).ClrBoxed;

I'll still mark this ticket as "missing feature" because we want to return a delegate that doesn't expose the internal stuff.

[fholm]

This if fixed in commit a6aecac0cb4 by adding a new function to the Hosting.CSharp.Context object (C#) and the Hosting.FSharp module called GetFunctionAs(name) / getFunctionAs<'a> name.

var ctx = new IronJS.Hosting.CSharp.Context();

ctx.Execute(@"
    function multiply(a, b) {
        return a * b;
    }
");


var multiply = ctx.GetFunctionAs<Func<double, double, double>>("multiply");
var result = multiply.Invoke(4.0, 4.0);

[dahlbyk]

Haven't had a chance to try it yet, but thanks for the quick response on this!