[Ironruby-core] A nicer syntax for generic extension methods

Ryan Riley ryan.riley at panesofglass.org
Tue Feb 2 17:38:44 EST 2010


That's fantastic, Tomas, thanks! Is there any way to pass a block, lambda,
or Proc into the slot for the delegate, or perhaps a way to create a .NET
delegate (or Expression) from a block, lambda, or Proc?

Thanks,

Ryan Riley

Email: ryan.riley at panesofglass.org
LinkedIn: http://www.linkedin.com/in/ryanriley
Blog: http://wizardsofsmart.net/
Twitter: @panesofglass
Website: http://panesofglass.org/


On Tue, Feb 2, 2010 at 1:36 AM, Tomas Matousek <Tomas.Matousek at microsoft.com
> wrote:

> Actually, you can add Ruby methods to List<T> … IronRuby type system does
> some magic for you J:
>
>
>
> >>> include System::Collections::Generic
>
> => Object
>
> >>> List[Fixnum].included_modules
>
> => [System::Collections::Generic::List[T],
> System::Collections::Generic::IList[Fixnum],
> System::Collections::Generic::IList[T],
> System::Collections::Generic::ICollection[Fixnum],
> System::Collections::Generic::ICollection[T],
> System::Collections::Generic::IEnumerable[Fixnum],
> System::Collections::Generic::IEnumerable[T],
> System::Collections::IEnumerable, Enumerable, System::Collections::IList,
> System::Collections::ICollection, System::Collections::Generic, Kernel]
>
>
>
> As you can see the List<> generic type definition is treated as a module
> that is mixed in each of its instantiations. Although there are no
> predefined methods on it you can open it and add some. First we need to get
> Ruby class for List<T>. If you index System.Collections.Generic.List by a
> fixnum instead of a class/module you’ll get the generic definition of arity
> 1. Let’s name it ListOfT:
>
>
>
> >>> ListOfT = List[1]
>
>
>
> And then we can open it up:
>
>
>
> >>> module ListOfT
>
> ...   def size
>
> ...     count
>
> ...   end
>
> ... end
>
> => nil
>
> >>> l = List[Fixnum].new
>
> => []
>
> >>> l.add(1)
>
> => nil
>
> >>> l.add(2)
>
> => nil
>
> >>> l.size
>
> => 2
>
>
>
> Tomas
>
>
>
>
>
> *From:* ironruby-core-bounces at rubyforge.org [mailto:
> ironruby-core-bounces at rubyforge.org] *On Behalf Of *Orion Edwards
> *Sent:* Monday, February 01, 2010 6:31 PM
> *To:* ironruby-core at rubyforge.org
> *Subject:* Re: [Ironruby-core] A nicer syntax for generic extension
> methods
>
>
>
> IIRC you can open "concrete" generics, but not "open" ones: In plain
> english this means you can add methods to List<string> but not List<T>.
>
>
>
> This is essentially because List<T> isn't a real type in the CLR, it's
> basically some metadata that can be used to build a real type when the T is
> supplied.
>
>
>
> You could as an alternative add methods to the underlying non-generic
> IEnumerable interface, but then you'd have to do some run-time reflection to
> figure out that your List is actually a List<string>... This is probably not
> nice.
>
>
>
> In theory when CLR4 lands and has support for co/contra variant generics,
> List<object> should match List<string> and everything else, but I don't know
> if IronRuby would also work for this?
>
>
>
> Good luck
>
> On Tue, Feb 2, 2010 at 7:52 AM, Ryan Riley <ryan.riley at panesofglass.org>
> wrote:
>
> I have been trying to figure out how to Rubify generic extension methods
> for use with the likes of Rx, Open XML SDK, etc. Ivan went over it a bit
> with me this weekend, but I'm still having difficulty including a module
> within a .NET type. Is that even possible?
>
>
>
> ...
>
>
>
> The questions I'm not able to answer are:
>
>    1. Can I somehow open up a .NET class, say
>    System::Collections::Generic::List[T] and include the EnumerableExtensions?
>    So far, I'm finding that's a no.
>    2. How do I hook in the included(base) method above? I'm assuming
>    that's a one-time call, but I don't see anywhere that it's called when a
>    module is included. Do I need to use a before_filter or perform that action
>    at the beginning of the linq_select method?
>
>
>
> Thanks!
>
>
> Ryan Riley
>
> Email: ryan.riley at panesofglass.org
> LinkedIn: http://www.linkedin.com/in/ryanriley
> Blog: http://wizardsofsmart.net/
> Twitter: @panesofglass
> Website: http://panesofglass.org/
>
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