Question

I am trying to create a model for a ruby on rails project that builds relationships between different words. Think of it as a dictionary where the ‘Links’ between two words shows that they can be used synonymously. My DB looks something like this:

Words ---- id  Links ----- id word1_id word2_id 

How do I create a relationship between two words, using the link-table. I’ve tried to create the model but was not sure how to get the link-table into play:

class Word < ActiveRecord::Base   has_many :synonyms, :class_name => 'Word', :foreign_key => 'word1_id' end 

Answer 1

In general, if your association has suffixes such as 1 and 2, it’s not set up properly. Try this for the Word model:

class Word < ActiveRecord::Base   has_many :links, :dependent => :destroy   has_many :synonyms, :through => :links end 

Link model:

class Link < ActiveRecord::Base   belongs_to :word   belongs_to :synonym, :class_name => 'Word'    # Creates the complementary link automatically - this means all synonymous   # relationships are represented in @word.synonyms   def after_save_on_create     if find_complement.nil?       Link.new(:word => synonym, :synonym => word).save     end   end    # Deletes the complementary link automatically.   def after_destroy     if complement = find_complement       complement.destroy     end   end    protected    def find_complement     Link.find(:first, :conditions =>        ['word_id = ? and synonym_id = ?', synonym.id, word.id])   end end 

Tables:

Words ---- id  Links ----- id word_id synonym_id