Question

Rails: 3.2.11

I have this module in lib and required in application.rb. I’d like to make the constant FORBIDDEN_USERNAMES available throughout the app. The constant is an array of values generated from the routes. I can’t make this an initializer because the routes haven’t been loaded yet.

What I have below doesn’t work as FORBIDDEN_USERNAMES returns an empty array.

# in lib
module ForbiddenUsernames    
  def self.names
    Rails.application.reload_routes!
    all_routes = Rails.application.routes.routes

    all_names = Array.new
    all_routes.each do |route|
      # populate all_names array
    end
    all_names.uniq
  end
end

FORBIDDEN_USERNAMES = ForbiddenUsernames.names
# when ForbiddenUsernames.names is called by itself, it does not return [] or nil

Throughout the app, how do I make it so that I can just use FORBIDDEN_USERNAMES? Thank you!

Answer 1

I don’t understand why you want this to be a constant. It seems to me you could use memoizable behavior.

# Wherever in your controller. Add helper_method if you need in the view (but would seem wrong)
def forbidden_usernames
  @forbidden_usernames ||= ForbiddenUsernames.names
end
helper_method :forbidden_usernames

ForbiddenUsernames.names will be called if @forbidden_usernames is nil, so it only happen once.

Update

# app/models/user.rb
def forbidden_usernames
  @forbidden_usernames ||= ForbiddenUsernames.names
end

def validate_not_forbidden
  !forbidden_usernames.include?(self.name)
end

If ever you need this functionality in more than one model, use modules. You can also have the forbidden_usernames memoized method in the module itself.

module ForbiddenUsernames    
  def self.names
    @forbidden_names ||= self.populates_all_names
  end

  protected

  def populate_all_names
    Rails.application.reload_routes!
    all_routes = Rails.application.routes.routes

    all_names = Array.new
    all_routes.each do |route|
      # populate all_names array
    end
    all_names.uniq
  end
end