Returning a CLR type from IronRuby

Question

Hi,

I am trying to return a CLR object from Iron Ruby.

I have the following CLR type defined in C#

public class BuildMetaData
{
    public string Description { get; set; }
}

I have the following IronRuby file:

$:.unshift(File.dirname(__FILE__) + '/../bin/Debug') 
require 'mscorlib'
require 'Horn.Core.DSL.Domain'

class MetaDataFactory
    def return_meta_data()
     meta = Horn::Core::DSL::Domain::BuildMetaData.new
     meta.Description = "A description of sorts"
        meta
    end
end

I have the following test that is failing:

[Fact]
public void Then_a_build_metadata_object_is_returned()
{                       
    var engine = Ruby.CreateEngine();

    engine.ExecuteFile("test.rb");

    var code = String.Format("{0}.new.method :{1}", "MetaDataFactory", "return_meta_data");

    var action = engine.CreateScriptSourceFromString(code).Execute();

    var result = (BuildMetaData)engine.Operations.Call(action);

    Assert.Equal(result.Description, "A description of sorts");
}

It fails when trying to cast the object returned from IronRuby.

I get the following error message:

[A]Horn.Core.DSL.Domain.BuildMetaData cannot be cast to [B]Horn.Core.DSL.Domain.BuildMetaData. Type A originates from 'Horn.Core.DSL.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'LoadNeither' at location 'C:\Projects\horn\branches\rubydsl\src\Horn.Dsl.Specificatioin\bin\Debug\Horn.Core.DSL.Domain.dll'. Type B originates from 'Horn.Core.DSL.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'Default' at location 'C:\Users\paul.cowan\AppData\Local\Temp\1vt2usw2.rxf\Horn.Dsl.Specificatioin\assembly\dl3\1d5ed945\7c19e429_1a97c901\Horn.Core.DSL.Domain.DLL'.

Is it possible to return CLR types from Iron Ruby

Answer 1

Rather than getting the method with a specially crafted string of Ruby, and then using C# to call the method, the preferred way to call into Ruby code from C# is the following:

var engine = IronRuby.Ruby.CreateEngine()
engine.ExecuteFile("test.rb")
var klass = engine.Runtime.Globals.GetVariable("MetaDataFactory")
var instance = engine.Operations.CreateInstance(klass)
engine.Operations.InvokeMember(instance, "return_meta_data")

~Jimmy

Answer 2

Actually it was all down to shadow copying.

My code ended up looking like this:

[Fact]
public void Then_the_object_should_be_accessible_in_csharp()
{                       
    var engine = Ruby.CreateEngine();

    engine.Runtime.LoadAssembly(typeof (BuildMetaData).Assembly);

    engine.ExecuteFile(buildFile);

    var klass = engine.Runtime.Globals.GetVariable("MetaDataFactory");

    var instance = (RubyObject)engine.Operations.CreateInstance(klass);

    //You must have shadow-copying turned off for the next line to run and for the test to pass.
    //E.g. in R# "ReSharper/Options/Unit Testing/Shadow-Copy Assemblies being tested" should be un-checked.
    var metaData = (BuildMetaData)engine.Operations.InvokeMember(instance, "return_meta_data");

    Assert.Equal(metaData.Description, "A description of sorts");

    Assert.Equal(metaData.Dependencies.Count, 1);
}

But if I turned off shadow-copying from the R# test runner then the test now passes.