From a personal experience, In a recent interview for a rails developer position, i was asked to implement something simple but tricky. eg:
"We need an application to create a post, comments, and replies with only two tables, how will you approach it."
- All i could think of was creating a boolean column in comments table to trigger replies. After the session, the interviewer gave me a straight tip on what he expected and that's single table inheritance(STI).
- We've 'Posts table' and 'Comments table', after generating our models and migrating, we can create another class 'Replies' to inherit from 'Comments'. eg
Post model
Rails generate model post title:string
above we generate a model Post with a title column.
Comments model
Rails generate model comment title:string type:string
above is a comments model with title and type, you might be wondering why type? well, we need a column to hold replies type. creating a reply will be saved as a type.
let's generate a replies model.
Rails generate model reply --parent=Comment
Yes, about the flag used --parent a normal model inherits from active record by default but here we want our model to inherit from Comment model, adding the flag generate something like this
class Reply < Comment
end
we can comments and replies
# comment
comment = Comment.create(title: "hello comment")
reply
# reply = Reply.create(title: "hello title")
Reply SQL looks like
INSERT INTO "comments" ("type", "title") VALUES ('Reply', 'hello title')
You should always try to avoid Single Table Inherency(STI), it makes models associations complicated
Top comments (1)
i agree