Comments on Liquid Development: Twisting and Shaping DSLs using Ruby Metaprogrammi...

I must admit the registry confuses me too, how and...

2008-03-05T12:16:00.000+01:00

I must admit the registry confuses me too, how and why would it self register, does it need to do this.

Although I understand most the "register_with_glob...

2008-03-05T12:14:00.000+01:00

Although I understand most the "register_with_global_repository" self registry confuses me a little, and could you use this type of programme under any naming syntax.

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2007-04-25T11:06:00.000+02:00

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Gabriele kicked my ass at: http://riffraff.blogsom...

2006-06-08T11:19:00.000+02:00

Gabriele kicked my ass at: http://riffraff.blogsome.com/2006/05/02/metaprogramming-breakfast/

I'll provide a sample impl ASAP, sray tuned :)

2006-05-02T17:13:00.000+02:00

I'll provide a sample impl ASAP, sray tuned :)

Hi Hyperstruct, you are right. I pushed it too fa...

2006-05-01T21:42:00.000+02:00

Hi Hyperstruct, you are right. I pushed it too far and the trailing dot is not very DSL like.. I should have stopped just a little bit earlier.

BlankSlate is cool, it removes most methods from a class to give free rein to method_missing users. You are right, it is appropriate to use that too.

###############Killing the New###############def R...

2006-05-01T21:32:00.000+02:00

###############
Killing the New
###############

def Recipe *args
Recipe.new *args
end

now you can just do Recipe(..) and you get a recipe. I call this a Concept Declarator.

In a future post I'll show how to do it semi-autmatically with metaprogramming.

How do you get rid of 'new', as mentioned at the t...

2006-05-01T20:23:00.000+02:00

How do you get rid of 'new', as mentioned at the top?

i.e.
Recipe("italian breakfast").caffe 1, :macchiato

How do you get rid of 'new', as mentioned at the t...

2006-05-01T20:22:00.000+02:00

How do you get rid of 'new', as mentioned at the top?

i.e.
Recipe("italian breakfast").caffe 1, :macchiato

I'm afraid that the parentheses and the trailing d...

2006-05-01T17:43:00.000+02:00

I'm afraid that the parentheses and the trailing dot in:

"italian breakfast".consists_of.
caffe (1 , :macchiato ).
cornetto (1, :cioccolato)

...spoil most most of the good work before it. I'd probably go for
the usual instance_eval trick with something like:

"italian breakfast".consists_of {
caffe 1, :macchiato
cornetto 1, :cioccolato
}

recipe? "italian breakfast"

(Sample mess, I mean, implementation at the bottom.)

Also when playing with method missing you might want to start with a blank slate, someone might always decide to #freeze a cornetto or do
something we wouldn't expect with a #hash. :-)

require 'singleton'
class RecipeCollection
include Singleton

def self.<<(recipe)
instance << recipe
end

def self.lookup(title)
instance.lookup(title)
end

def <<(recipe)
@recipes ||= []
@recipes << recipe
end

def lookup(title)
@recipes.find { |r| r.title == title }
end
end

class Recipe
def initialize(title, &ingredients_desc)
@title, @ingredients = title, {}
instance_eval(&ingredients_desc)
RecipeCollection << self
end
attr_reader :title

def method_missing(id, *args)
@ingredients[id.to_s] = args
end

def to_s
@title + ":\n" +
@ingredients.collect do |name, description|
description.join(' ') + ' ' + name
end.join("\n")
end
end

class String
def consists_of(&ingredients_desc)
Recipe.new(self, &ingredients_desc)
end
end

def recipe?(name)
puts RecipeCollection.lookup(name)
end

Very inventive Gabriele!so.. three, two and so on ...

2006-04-30T20:57:00.000+02:00

Very inventive Gabriele!

so.. three, two and so on are implicit methods that get caught by method_missing. 'of' is a nil variable that doen't get used.. or did you miss some "." when copying the code here?

or is it supposed to be three(of(sliced_bread()) with a cascade of method_missings being called?

Can you give us a sample implementation?

Brilliant! Your insightful explanation is extremel...

2006-04-30T17:30:00.000+02:00

Brilliant! Your insightful explanation is extremely clear, I've just realized that I still have a lot to learn about the great Ruby! :)

I was thinking of taking yet another route: (brack...

2006-04-30T11:02:00.000+02:00

I was thinking of taking yet another route:
(brackets, fur to non-meaningfulness of do..end in this case)

shopping_list_for "BLT sandwiches" {
three of sliced_bread
two of lettuce
six of tomatoes
four of bacon
}

This requires you to turn down $VERBOSE or you'll get warnings.
Obviously you can use add #of to Fixnum to sidestep the issue, or you can remove it completely.

Eliminating semicolons is easy once you evaluate the block in a context where method_missing is just returning the called symbol.