How to Implement Multi-Table Inheritance for Posts in Laravel Using Eloquent?

Implementing Single Table Inheritance in Laravel Using Eloquent

Scenario:

You have a model named Post and want to divide posts into two types: articles and questions, using inheritance.

Single Table Inheritance

Single table inheritance involves maintaining all types in the same table, with a column to distinguish between them. While this approach can be simpler, it can result in a lot of NULL values due to columns that are not applicable to all types.

Multi Table Inheritance

Multi table inheritance is a cleaner approach that splits the data into multiple tables. A postable column indicates the type of post, and a postable_id references the primary key in the corresponding table.

Implementing Multi Table Inheritance in Eloquent

Post Model:

Add a postable relationship to the Post model, which will be a polymorphic relationship:

<code class="php">class Post extends Eloquent {
    public function postable() {
        return $this->morphTo();
    }
}</code>

Question and Article Models:

Create separate models for each post type and establish the relationship with the Post model:

<code class="php">class Question extends Post {
    public function post() {
        return $this->morphOne('Post', 'postable');
    }
}</code>

<code class="php">class Article extends Post {
    public function post() {
        return $this->morphOne('Post', 'postable');
    }
}</code>

Usage:

• Retrieve all posts: Post::all().
• Retrieve all questions: Question::all().
• Access related question properties from a Post object: $post->postable->question_column.
• Determine the post type: get_class($post->postable).

• Create a new question:

  • Create both a Question and Post object.
  • Link them using $question->post()->save($post).

Recommendation:

For a more user-friendly implementation, it is recommended to consolidate the model creation logic into reusable functions within each model class.

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