module SimpleColumn

Purpose: Create dynamic modules which define dynamic methods for scopes based on a dynamic array of column names

Library Usage:

class Monkey < ActiveRecord::Base

include SimpleColumn::Scopes.new(:for_user_id, :for_seller_id, ... etc)
# => for_user_id, and for_seller_id scopes are added to the model,
      and they query on the user_id and seller_id columns, respectively

Constants

SCOPE_PREFIX
SCOPE_PREFIX_REGEX

Public Class Methods

new(*scope_names) click to toggle source

# File lib/simple_column/scopes.rb, line 34
def initialize(*scope_names)
  # => { :for_user_id => "user_id" }
  @simple_scope_names_hash = scope_names.map(&:to_sym).each_with_object({}) do |scope_name, memo|
    # method name definitions are best with symbols, and gsub only works on strings.
    memo[scope_name] = scope_name.to_s.sub(SimpleColumn::SCOPE_PREFIX_REGEX, '')
  end
  # Raising an error here is safe, because it will fail on boot if there is an implementation problem (early!)
  unless (bad_scopes = @simple_scope_names_hash.select { |scope_name, column_name| scope_name.to_s == column_name }).blank?
    bad_scope_names(bad_scopes)
  end
end

to_mod(scope_names_hash) click to toggle source

returns an anonymous (nameless) Module instance

# File lib/simple_column/scopes.rb, line 20
def to_mod(scope_names_hash)
  Module.new do
    scope_names_hash.each do |scope_name, column_name|
      # methods are defined at the instance level, so will become class methods when this module extends a class.
      define_method(scope_name) do |value|
        where(column_name => value)
      end
    end
  end
end

Public Instance Methods

bad_scope_names(bad_scopes) click to toggle source

# File lib/simple_column/scopes.rb, line 61
def bad_scope_names(bad_scopes)
  raise ArgumentError, "SimpleColumn::Scopes need to be named like #{SimpleColumn::SCOPE_PREFIX}<column_name>, but provided #{bad_scopes.keys}"
end

included(base) click to toggle source

# File lib/simple_column/scopes.rb, line 46
def included(base)
  # How to do this without breaking the build?
  # if ActiveRecord::Base.connection.active?
  #   # Invoking this requires that a database be present.
  #   unless (bad_scopes = @simple_scope_names_hash.reject { |_, column_name| base.column_names.include?(column_name) }).blank?
  #     bad_scope_names(bad_scopes)
  #   end
  # end
  anonymous_module = SimpleColumn.to_mod(@simple_scope_names_hash)
  # This will override methods defined in the including class with the same name, if any,
  #   because extend has the effect of injecting the code into the bottom of the class file, lexically,
  #   making these definitions highest priority.
  base.send(:extend, anonymous_module)
end