How to factor this code ? (not trivial)

[Nicolas Desprès]

Hi,

I'm having trouble to factor some simple code. Since, I have been stuck for several days now I ask the question here.

# Beginning of code

module DefWithName

  def integer(name, options = {})

    store_result name, MyInteger.new(options)

  end

  def id(name)

    integer(name, an_options: true)

  end

end

module DefWithoutName

  def integer(options = {})

    store_result MyInteger.new(options)

  end

  def id

    integer(an_options: true)

  end

end

class A; include DefWithName; end

class AA; include DefWithName; end

class B; include DefWithoutName; end

class BB; include DefWithoutName; end

# End of code

Constraints:

- The "id" function has to call "integer" and not "store_result" because it may be defined as a plugin.

- The functions must still raise ArgumentError as they already do.

Any ideas?

Regards,

-Nico

[Frederick Cheung]

On Monday, March 4, 2013 12:59:23 PM UTC, Nicolas Desprès wrote:
> Hi,

>
>
> Constraints:
> - The "id" function has to call "integer" and not "store_result" because it may be defined as a plugin.
> - The functions must still raise ArgumentError as they already do.
>
>

Could you give some examples of what you're trying to do or problems you've run into? You've posted some code but haven't described how you'll be using it and in what way it isn't adequate.In fewer words: I don't see what your question is.

Fred

[Nicolas Desprès]

Thanks for replying.

Yes sorry. I realize that some context is missing.

# I am writing an API where the users are allowed to write something like that:

FooContextWithName.new.eval do |o|

  o.integer "id", an_option: true    # [1]

  o.integer "foo", an_option: true  # [2]

  o.bar "a_name" do |o|

    o.integer an_option: true         # [3]

  end

end

# I would like that users are able to factor [1] and [2] by writing a small plugin like this:

module MyHelpers

  def id(name = "id")

     integer name, an_option: true

  end

end

MyLib.add_helpers(MyHelpers)  # add_helpers would be defined appropriately

# To factor [3] users should be able to write something like that:

module MyHelpers

  def id

     integer an_option: true

  end

end

# To implement this API I have something like this

module DefWithName

  def integer(name, options = {})

    store_result name, MyInteger.new(options)

  end

end

module DefWithoutName

  def integer(options = {})

    store_result MyInteger.new(options)

  end

end    

class FooWithName < BasicObject

  include DefWithName

  def store_result(name, object)

    @props[name] = object

  end

end

class BarWithoutName < BasicObject

  include DefWithoutName

  def store_result(object)

    @items << object

  end

end

===========================

My goal is to provide a way for users to write their "id" method once and to work in both cases.

I am thinking about something like that:

def id(*args)

  if name_required?

    name = name_given? ? given_name : "id"

  end

  integer name, an_option: true

end

def integer(*args)

  value = MyInteger.new(options)

  if name_required?

    if name_given?

      store_result given_name, value

    else

      raise ArgumentError

    end

  else

    if name_given?

      raise ArgumentError

    end

    store_result value

  end

end

where "name_required?", "given_name" and "name_given?" would be defined appropriately based on the arguments passed to the method.

I hope this is clearer now.

--
Nicolas Desprès

[Nicolas Desprès]

I finally found a good way to factor this.

Instead of having two modules DefWithoutName and DefWithName I have only one:

module BasicDef

  def integer(name, options = {})

    store_result name, MyInteger.new(options)

  end

end

Then I use a proxy for evaluation that will

- in the case of "with name" will call directly the target method and pass it all the arguments

- in the case of "without name" will call the target method by passing "nil" as first arguments and then the rest of the arguments.

The proxy checks when the target method requires a name as first argument using the Method#parameters method. 

--
Nicolas Desprès