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Active Record Associations
I am currently working on my first Ruby/Sinatra Application for my online software engineering program. I wanted to share what I learned about Active Record Associations and all the built in methods we get access to using it.
has_many
An instance of one class that owns many instances of another class. This class must pluralize the has many instance method to get access to all the instances it owns. A User has many recipes
class Actor < ActiveRecord::Base has_many :charactersendclass Show < ActiveRecord::Base has_many :charactersendThe has_many association gives us access to 17 methods
actorsactors<<(object, ...)actors.delete(object, ...)actors.destroy(object, ...)actors=(objects)actor_idsactor_ids=(ids)actors.clearactors.empty?actors.sizeactors.find(...)actors.where(...)actors.exists?(...)actors.build(attributes = {})actors.create(attributes = {})actors.create!(attributes = {})actors.reload belongs_to
An instance that is owned by the has many class. We will state the belongs to method as singular to retrieve the relationship to the unique owner class. A Recipe belongs to one owner
class Character < ActiveRecord::Base belongs_to :actor belongs_to :showendTo ensure reference consistency, add a foreign key to the owner column of the owned table migration.
class CreateRecipes < ActiveRecord::Migration[6.1] def change create_table :characters do |t| t.belongs_to :actor t.belongs_to :show end endendThe belongs_to association gives us access to 8 methods
charactercharacter=(character)build_character(attributes = {})create_character(attributes = {})create_character!(attributes = {})reload_charactercharacter_changed?character_previously_changed? has_many through:
This creates a relationship bridge between two owner classes' and the owned/connecting class
class Show < ActiveRecord::Base has_many :characters has_many :actors, through: :charactersendOriginal Link: https://dev.to/walktheworld/active-record-associations-15go
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