Polymorphic relationships in Laravel - Mini Project: Build & Apply

Polymorphic Relationships in Laravel

📖 Scenario: You are building a simple blog system where users can comment on both posts and videos. Instead of creating separate comment tables for posts and videos, you will use Laravel's polymorphic relationships to keep comments in one table and link them to either posts or videos.

🎯 Goal: Create a Laravel polymorphic relationship where Comment can belong to either a Post or a Video. You will set up the models, migrations, and relationships step-by-step.

📋 What You'll Learn

Create migrations for posts, videos, and comments tables

Define polymorphic relationship methods in Post, Video, and Comment models

Use Laravel Eloquent conventions for polymorphic relations

Link comments to posts or videos using polymorphic keys

💡 Why This Matters

🌍 Real World

Polymorphic relationships let you reuse one comments table for different content types like posts and videos, saving database space and simplifying code.

💼 Career

Understanding polymorphic relationships is important for Laravel developers building flexible, scalable applications with shared features like comments, tags, or images.

1

Create migrations for posts and videos tables

Create two migrations: one for a posts table with columns id and title, and one for a videos table with columns id and title. Use Laravel's schema builder syntax.

Laravel

// Create migration for posts table
// Create migration for videos table
// Your code here

Need a hint?

Use Schema::create with a closure that defines $table->id() and $table->string('title') for both tables.

2

Create migration for comments table with polymorphic columns

Create a migration for a comments table with columns id, body, commentable_id, and commentable_type. Use Laravel's polymorphic columns naming convention.

Laravel

<?php
// Add migration for comments table with polymorphic columns
// Your code here

Need a hint?

Use $table->unsignedBigInteger('commentable_id') and $table->string('commentable_type') to set up polymorphic keys.

3

Define polymorphic relationship methods in models

In the Post and Video models, add a comments() method that returns $this->morphMany(Comment::class, 'commentable'). In the Comment model, add a commentable() method that returns $this->morphTo().

Laravel

<?php
// Add polymorphic relationship methods to Post, Video, and Comment models
// Your code here

Need a hint?

Use morphMany in Post and Video models, and morphTo in Comment model.

4

Attach comments to posts and videos in a controller example

In a controller method, create a Post and a Video. Then create a Comment for each by using the comments() relationship's create() method with ['body' => 'Your comment text'].

Laravel

<?php
// Create a Post and Video
// Add a comment to each using the comments() relationship
// Your code here

Need a hint?

Use create() on the comments() relationship to add comments linked to the post or video.