Forum: IronRuby Accessing the return value from a Dsl

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5b9872f3076db04cb2ffb516091d80d0?d=identicon&s=25 Paul Cowan (dagda1)
on 2009-03-16 11:51
Hi,

I am trying to create a Dsl which will have instances that live in
individual Dsl .rb files and then run them from the CLR.

I want to create and set the values of the Clr object in IronRuby and
then somehow have access to the CLR object after the .rb Dsl instance
file has run.

Here is my Clr object which is very simple at the moment:

namespace Horn.Core.Dsl
{
    public class BuildMetaData : IBuildMetaData
    {
        public string Description { get; set; }
    }
}

I have the following module which I am using to specify my Dsl and which
will create an instance of the BuildMetaData specified above:

module MetaBuilder
  module Dsl
    module Main
      attr_accessor :metadata
      def install(name, &block)
        @metadata = Horn::Core::Dsl::BuildMetaData.new
        yield self if block_given?
      end

      def description(desc)
         @metadata.Description = desc
      end

      def get_metadata
          @metadata
      end

    end
  end
end

include MetaBuilder::Dsl::Main

I somehow want to be able to get the @metadata property from the Clr
code after an instance of the Dsl has ran.

An instance of the Dsl looks like this currently:

install :horn do
  description "A .NET build and dependency manager"
end

My C# code looks like this currently:

var engine = Ruby.CreateEngine();
engine.Runtime.LoadAssembly(typeof(BuildMetaData).Assembly);
engine.ExecuteFile(buildFile);
var klass = engine.Runtime.Globals.GetVariable("get_metadata");

Is there anyway I can get at the @metadata property without having to
pollute the Dsl instance?

For that matter is my approach reasonable or is there perhaps a better
way?

Thanks in advance

Paul
5b9872f3076db04cb2ffb516091d80d0?d=identicon&s=25 Paul Cowan (dagda1)
on 2009-03-17 00:40
Hi,

For anyone who is interested, I managed to solve this by creating a
singleton to house an instance of the BuildMetaData class.

My Ruby code ended up looking like this:

module MetaBuilder
  module Dsl
    module Main

      def install(name, &block)
        yield self if block_given?
      end

      def get_from(name, url)
        puts name
        puts url
      end

      def description(desc)
         meta.metadata.Description = desc
      end

      class MetaDataAccessor
        attr_accessor :metadata

        private
        def initialize
          @metadata = Horn::Core::Dsl::BuildMetaData.new
        end

        public
        def self.instance
          @@instance ||= new
        end

        def self.get_metadata
            @metadata
        end
      end
    end
  end
end

def meta
  MetaBuilder::Dsl::Main::MetaDataAccessor.instance
end

class ClrAccessor
  def get_build_metadata
    meta.metadata
  end
end

include MetaBuilder::Dsl::Main

I created the MetaDataAccessor to keep a singleton BuildMetaData
instance.

I could not work out the C# code to access a fully qualified class that
is nested in between modules so I created the ClrAccessor class to
provide access from the Clr.

My C# code ended up looking like this:

var engine = Ruby.CreateEngine();
engine.Runtime.LoadAssembly(typeof(BuildMetaData).Assembly);
engine.ExecuteFile(buildFile);
var klass = engine.Runtime.Globals.GetVariable("ClrAccessor");
var instance = engine.Operations.CreateInstance(klass);
buildMetaData = (BuildMetaData)engine.Operations.InvokeMember(instance,
"get_build_metadata");

I am fairly sure there is an easier way but for me it is progress.

Any input into this "round the houses" approach would be appreciated.

Cheers

Paul

Paul Cowan wrote:
> Hi,
>
> I am trying to create a Dsl which will have instances that live in
> individual Dsl .rb files and then run them from the CLR.
>
> I want to create and set the values of the Clr object in IronRuby and
> then somehow have access to the CLR object after the .rb Dsl instance
> file has run.
>
> Here is my Clr object which is very simple at the moment:
>
> namespace Horn.Core.Dsl
> {
>     public class BuildMetaData : IBuildMetaData
>     {
>         public string Description { get; set; }
>     }
> }
>
> I have the following module which I am using to specify my Dsl and which
> will create an instance of the BuildMetaData specified above:
>
> module MetaBuilder
>   module Dsl
>     module Main
>       attr_accessor :metadata
>       def install(name, &block)
>         @metadata = Horn::Core::Dsl::BuildMetaData.new
>         yield self if block_given?
>       end
>
>       def description(desc)
>          @metadata.Description = desc
>       end
>
>       def get_metadata
>           @metadata
>       end
>
>     end
>   end
> end
>
> include MetaBuilder::Dsl::Main
>
> I somehow want to be able to get the @metadata property from the Clr
> code after an instance of the Dsl has ran.
>
> An instance of the Dsl looks like this currently:
>
> install :horn do
>   description "A .NET build and dependency manager"
> end
>
> My C# code looks like this currently:
>
> var engine = Ruby.CreateEngine();
> engine.Runtime.LoadAssembly(typeof(BuildMetaData).Assembly);
> engine.ExecuteFile(buildFile);
> var klass = engine.Runtime.Globals.GetVariable("get_metadata");
>
> Is there anyway I can get at the @metadata property without having to
> pollute the Dsl instance?
>
> For that matter is my approach reasonable or is there perhaps a better
> way?
>
> Thanks in advance
>
> Paul
Cb51033949ffccd982ae32c9f890f25a?d=identicon&s=25 Tomas Matousek (Guest)
on 2009-03-17 18:40
(Received via mailing list)
What scope you would like the instance of BuildMetaData to appear in?
There are basically 2 possibilities:

1) global

Any global Ruby constants will appear in Runtime.Globals dictionary. So
you can just assign the instance into a constant:

MyInstance = Horn::Core::Dsl::BuildMetaData.new

and get it back in C# via Globals.GetVariable("MyInstance")

2) in a DLR execution scope

This is a little bit more tricky since Ruby doesn't have a concept of
execution scopes (unlike Python that has modules). IronRuby has a hook
in method definition that publishes a method defined on a "main" object
into the DLR scope. The "main" object is a singleton of Object class
that Ruby creates for top-level scope self:

> ruby -e 'p self'
main

In IronRuby you can do this:

foo.rb:
def self.my_method
  123
end

C#:
var scope = engine.ExecuteFile("foo.rb");
var my_method = scope.GetVariable<Func<int>>("my_method")
Console.WriteLine(my_method());

I'm still looking for improvements to DLR scope interop, so this might
actually change in future.

Tomas
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