What are the main Rails associations?
Rails supports six types of associations: belongs_to. has_one. has_many.
What is Has_many in Ruby?
Ruby on Rails ActiveRecord Associations has_many A has_many association indicates a one-to-many connection with another model. This association generally is located on the other side of a belongs_to association. This association indicates that each instance of the model has zero or more instances of another model.
What is polymorphic association in Rails?
In Ruby on Rails, a polymorphic association is an Active Record association that can connect a model to multiple other models. For example, we can use a single association to connect the Review model with the Event and Restaurant models, allowing us to connect a review with either an event or a restaurant.
What is a Rails model?
A Rails Model is a Ruby class that can add database records (think of whole rows in an Excel table), find particular data you’re looking for, update that data, or remove data. These common operations are referred to by the acronym CRUD–Create, Remove, Update, Destroy.
What is Rails Activerecord?
Rails Active Records provide an interface and binding between the tables in a relational database and the Ruby program code that manipulates database records. Each Active Record object has CRUD (Create, Read, Update, and Delete) methods for database access.
What does Belongs_to mean?
foreign key
belongs_to means that the foreign key is in the table for this class. So belongs_to can ONLY go in the class that holds the foreign key.
How is polymorphic association set up in Rails?
The basic structure of a polymorphic association (PA)sets up 2 columns in the comment table. (This is different from a typical one-to-many association, where we’d only need one column that references the id’s of the model it belongs to). For a PA, the first column we need to create is for the selected model.
What are the types of associations in rails?
Rails supports six types of associations: 1 belongs_to 2 has_one 3 has_many 4 has_many :through 5 has_one :through 6 has_and_belongs_to_many
How to declare an association in Ruby on rails?
Rails offers two different ways to declare a many-to-many relationship between models. The first way is to use has_and_belongs_to_many, which allows you to make the association directly: class Assembly < ApplicationRecord has_and_belongs_to_many :parts end class Part < ApplicationRecord has_and_belongs_to_many :assemblies end
What does has many mean in Ruby on rails?
A has_many association is similar to has_one, but indicates a one-to-many connection with another model. You’ll often find this association on the “other side” of a belongs_to association. This association indicates that each instance of the model has zero or more instances of another model.