rails model association using has_many: through

i have a lessons table and a tags table. i associate both of the them using a has_many :through relationship and my middle table is tags_relationship.rb

class Lesson < ActiveRecord::Base
   attr_accessible :title, :desc, :content, :tag_name
   belongs_to :user
 
   has_many  :tag_relationships
   has_many  :tags, :through => :tag_relationships
 end
 
 class Tag < ActiveRecord::Base
   attr_accessible :name
 
   has_many :tag_relationships
   has_many :lessons, :through => :tag_relationships
 end
 

in one of my views, im trying to create a a virtual attribute. i have...

    <div class="tags">
         <%= f.label :tag_name, "Tags" %>
         <%= f.text_field :tag_name, data: { autocomplete_source: tags_path} %>
     </div>
 

but my lessons table doesn't have that attribute, tag_name, so it calls my method instead

    def tag_name
        ????????
     end
 
     def tag_name=(name)
         self.tag = Tag.find_or_initialize_by_name(name) if name.present?
     end
 

however im not sure what to put inside the ????????. im trying to refer the :name attribute inside my tags table.

back then i used a has_many and belongs_to relationship. my lesson belonged to a tag (which was wrong) but i was able to write...

tag.name
 

and it worked. but since its a has_many :through now, im not sure. i tried using tags.name, Lessons.tags.name, etc but i cant seem to get it to work. how can i refer to the tags table name attribute? thank you

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