Forum: IronRuby Creating RubySymbols in C#

Hello,

I'm attempting to write a method in C# that is called by IronRuby to
speed up an existing script, and I call it like this:

  foo :limit => 5, :offset => 10

How would I go about accessing these objects from C#? I'm trying
something like this:

void foo(Hash options){
  int limit = (int)options[new RubySymbol("limit")];
  ...
}

However this doesn't work since RubySymbols constructor is private.
How would I go about getting the objects within the hash?

Thanks,
Rob

On Jun 23, 2011, at 11:45 AM, Rob Britton wrote:
>  ...
> }
>
> However this doesn't work since RubySymbols constructor is private.
> How would I go about getting the objects within the hash?


Rob, it's best to avoid depending on IronRuby built-in types in your 
.NET API unless you absolutely need to, as well as always having your 
.NET API's arguments be interface types, so both Ruby and .NET can call 
into them. If you did this:

    // C#
    public class MyClass {
        public void Foo(IDictionary args) {}
    }

You can still call it from Ruby:

    my_class.foo :limit => 5, :offset => 10

As for indexing, you can copy the provided Hash into a 
Dictionary<string, object> to provide string-based indexing:

    void Foo(IDictionary args) {
        var dict = new Dictionary<string, object>();
        foreach (DictionaryEntry a in args) dict[a.Key.ToString()] = 
a.Value;
        var limit = dict["limit"];
        var offset = dict["offset"];
        // do your stuff
    }


Another option (which I like more) is to write a Ruby wrapper around it 
to convert the keys to CLR strings:

    require 'MyClass' # load above assembly
    class MyClass # monkey-patch above .NET class
        alias :orig_foo :foo
        def foo(args)
            orig_foo args.inject({}){|i,(j,k)| i[j.to_clr_string] = k; i 
}
        end
    end

Then you wouldn't have to do the conversion in C#:

    void Foo(IDictionary dict) {
        var limit = dict["limit"];
        var offset = dict["offset"];
        // do your stuff
    }

I like the latter option best because you do what Ruby needs in Ruby; 
your .NET code assumes it's getting a CLR string rather than forcing it 
to be. However, it's not ideal as you have to copy the dictionary in 
both cases, but for an argument hash it's very unlikely to become an 
issue.

You'll notice that if you a .NET method that accepts a string, you can 
pass it a Ruby symbol; we do the conversion between Ruby symbols and 
.NET strings. However, we don't do conversions between generic 
arguments, especially with a Ruby Hash, were they keys could be 
different types. But we could convert a Hash to a statically typed 
Dictionary if all they keys are the same type; if you feel strongly 
about this please open a bug.

~Jimmy

Great, thanks! I don't feel strongly about it so I'll just put in a
little helper function to my .NET project to convert a Hash to a
Dictionary<string, object>. The monkey-patching method might not work
too well since there will be many functions that might use this
pattern, and having to monkey-patch every single one of them might get
annoying.