I did find some questions on SO about Rails associations that are somewhat like my question, but for the life of me I can't seem to understand how to use belongs_to multiple models.
Here's the table structure I intend to have:
User
id
Post
id
user_id #foreign key; a post belongs to a User aka "Who created this post"
Comment
id
user_id #foreign key; a comment belongs to a User aka "Who made this comment"
post_id #foreign key; a comment belongs to a Post aka "What post this comment is for"
And the associations:
User
has_many :posts
has_many :comments
Post
belongs_to :user
has_many :comments
Comment
belongs_to :user
belongs_to :post
Is this the correct approach?
Yes that is the correct approach.
While not always the "best" approach, Rails offers what's called a Polymorphic belongs_to association. It prevents you from defining a foreign key in the database because the xxx_id column is referencing an id in one of many possible tables while another column designates the name of that table's model, but it makes the relationship more explicit in Rails. Also, it restricts the model to only belong to one of the other models, as opposed to belonging to one or more, as it would happen using the setup of multiple foreign keys without some additional db magic.
来源：https://stackoverflow.com/questions/3911890/rails-belongs-to-many-models