Rails - Accessing module method in model

Question

So, I've read it all:

But I can't make it work. Here's my situation:

I have a calc_distance(place1, place2) method and an attribute places to my User model and I want to define a method calc_total_distance in the User model.

I want to access the calc_distance method through a Utils lib and not to load the whole utils when using it.

In /lib/utils.rb

module Utils
  def calc_distance a, b
    # Blah blah blah
  end
end

In /config/application.rb I have:

config.autoload_paths += %W(#{config.root}/lib)

In the console, I can do include Utils then calc_distance(place1, place2) and it works. But Utils::calc_distance(place1 place2) doesn't work ...

Extra-question is can I do this ?

Then in my User.rb model:

  def get_total_distance
    # Blah blah blah
    dist += calc_distance(place1, place2)
    # Blah blah blah
  end

returns me undefined method 'include' for #<User:0x00000006368278>

and

  def get_total_distance
    # Blah blah blah
    dist += Utils::calc_distance(place1, place2)
    # Blah blah blah
  end

returns me undefined method 'calc_distance' for Utils:Module

How can I achieve this, knowing that I really prefer the second method (which as I reckon, doesn't load the whole Utils module ...

can you try `include Utils` to user.rb? – maximus ツ Aug 08 '13 at 10:53 — maximus ツ, Aug 08 '13 at 10:53

score 3 · Answer 1 · answered Oct 26 '15 at 15:31

If you don't wan't to do mixin, but just to define some Utils' methods, then you can define the methods on module level (using self. prefix):

module Utils
  def self.calc_distance a, b
    # Blah blah blah
  end
end

and then call them this way:

Utils.calc_distance(place1, place2)

instead of

Utils::calc_distance(place1, place2)

score 0 · Answer 2 · answered Aug 08 '13 at 11:26

0

class Athlete < ActiveRecord::Base
  include Utils
  def get_total_distance
    # Blah blah blah
    dist += calc_distance(place1, place2)
    # Blah blah blah
  end
end

answered Aug 08 '13 at 11:26

Salil

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So I'd go for the first solution. No solution for doing Utils::calc_distance? Ain't I loading too many methods instead of only the one I need? – Augustin Riedinger Aug 08 '13 at 12:39
No, u can't load only one method of module. If you want like that you have to create different module with particular method – Salil Aug 08 '13 at 12:54
1

Ok, so when is it I should use `Module::method` as a syntax? – Augustin Riedinger Aug 09 '13 at 08:06

Rails - Accessing module method in model

2 Answers2