Flatiron-bnb: Associations

We're going to build Airbnb. Really. We're going to take this in steps. First let's work on our model associations and write migrations. This will be challenging, but doable. Take it slow and work together. Follow the model specs.

Before anything, note that when you generate models, controllers, etc, be sure to include this option, so that it skips tests (which we already have): --no-test-framework

Where to Begin

First think about the relations between all of the objects. Let's work through Users and Listings, and from there you should know some cool ActiveRecord tricks to get started on the rest.

We have a user object but a listing belongs to a specific type of user: a host. And the reservation (aka a trip) and a review both belong to a specific type of user: a guest. But we don't want to make two tables for a host and a guest. One way to do this is to create an association where, for example, a listing belongs to a host:

belongs_to :host

Active Record's belongs_to method is going to look for a table named "host", but that doesn't exist. Instead, we need to tell ActiveRecord which table host is referring to:

belongs_to :host, :class_name => "User"

The listings table is instead going to have a column for the foreign key called host_id.

Then on the User class, when we're creating a relationship with listings, where a user has_many listings, we need to specify which foreign key to look for on the listings table, otherwise, ActiveRecord is going to default to looking for a user_id when we named it host_id:

has_many :listings, :foreign_key => 'host_id'

Resources

Foreign key and Class Name AR class methods

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