Polymorphic relationships in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

Understanding polymorphic relation retrieval

Given a Laravel polymorphic relationship where a Comment model can belong to either a Post or a Video, what will be the output of the following code snippet?

$comment = Comment::find(1);
return get_class($comment->commentable);

Laravel

class Comment extends Model {
  public function commentable() {
    return $this->morphTo();
  }
}

// Assume comment with ID 1 belongs to a Post model instance

A App\Models\Post

B App\Models\Video

C Illuminate\Database\Eloquent\Relations\MorphTo

D App\Models\Comment

💡 Hint

The commentable relation returns the actual model instance the comment belongs to.

The morphTo relation dynamically returns the related model instance. Since comment ID 1 belongs to a Post, get_class returns the Post class name.

❓ state_output

intermediate

Counting polymorphic related models

In Laravel, if you have a Tag model that can belong to many different models via a polymorphic many-to-many relationship, what will be the count of tags returned by this code?

$post = Post::find(5);
return $post->tags()->count();

Assuming post ID 5 has 3 tags attached.

Laravel

class Post extends Model {
  public function tags() {
    return $this->morphToMany(Tag::class, 'taggable');
  }
}

A Throws an error because morphToMany is not defined

B 0

C 3

D Count of all tags in the database

💡 Hint

The count() method returns the number of related models for that specific post.

The morphToMany relation correctly fetches tags linked to the post. Since post ID 5 has 3 tags, count() returns 3.

📝 Syntax

advanced

Correct polymorphic relation definition

Which of the following is the correct way to define a polymorphic one-to-many relationship in a Laravel model named Photo that can belong to either a User or a Product?

A

public function imageable() {
  return $this->belongsTo();
}

B

public function imageable() {
  return $this->morphTo();
}

C

public function imageable() {
  return $this->morphMany();
}

D

public function imageable() {
  return $this->hasMany();
}

💡 Hint

The model that belongs to multiple other models uses morphTo().

In polymorphic one-to-many, the child model uses morphTo() to define the relation to its parent models.

🔧 Debug

advanced

Identify the cause of error in polymorphic relation

Given this Laravel model code, why does calling $comment->commentable cause an error?

class Comment extends Model {
  public function commentable() {
    return $this->morphOne(Post::class, 'commentable');
  }
}

A The Comment model must use morphMany instead

B The relation name 'commentable' is invalid

C The Post class does not exist

D Using morphOne instead of morphTo causes the error

💡 Hint

Check the direction of the polymorphic relation method used.

The child model should use morphTo() to define the polymorphic relation, not morphOne(). Using morphOne() here causes the error.

🧠 Conceptual

expert

Polymorphic relation database structure understanding

In Laravel polymorphic relationships, which two columns are essential in the related model's table to correctly store the polymorphic association?

A commentable_id and commentable_type

B id and type

C related_id and related_type

D morph_id and morph_type

💡 Hint

The column names combine the relation name and suffixes _id and _type.

Laravel uses {relation}_id and {relation}_type columns to store the ID and class name of the related model in polymorphic relations.