Polymorphic relationships in Laravel - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a polymorphic relation method in a Laravel model.

Laravel

public function image() {
    return $this->[1]('imageable');
}

Drag options to blanks, or click blank then click option'

AbelongsTo

BhasMany

CmorphTo

DhasOne

Attempts:

3 left

💡 Hint

Common Mistakes

Using hasMany or belongsTo instead of morphTo causes errors.

Forgetting to pass the relation name 'imageable' to the method.

In Laravel, the morphTo method defines the inverse of a polymorphic relation.

2fill in blank

medium

Complete the code to define a polymorphic relation in the Image model.

Laravel

public function imageable() {
    return $this->[1]();
}

Drag options to blanks, or click blank then click option'

AhasOne

BbelongsTo

ChasMany

DmorphTo

Attempts:

3 left

💡 Hint

Common Mistakes

Using belongsTo instead of morphTo breaks the polymorphic relation.

Adding parameters to morphTo in the child model is unnecessary.

The morphTo method is used in the polymorphic child model to access the parent model.

3fill in blank

hard

Fix the error in the polymorphic relation definition in the Post model.

Laravel

public function comments() {
    return $this->[1]('commentable');
}

Drag options to blanks, or click blank then click option'

AmorphMany

BhasMany

CbelongsToMany

DmorphTo

Attempts:

3 left

💡 Hint

Common Mistakes

Using hasMany instead of morphMany breaks polymorphic behavior.

Using morphTo is incorrect in the parent model for one-to-many.

Use morphMany in the parent model to define a polymorphic one-to-many relation.

4fill in blank

hard

Fill both blanks to complete the polymorphic relation in the Video model.

Laravel

public function tags() {
    return $this->[1]('taggable');
}

public function taggable() {
    return $this->[2]();
}

Drag options to blanks, or click blank then click option'

AmorphToMany

BbelongsToMany

CmorphTo

DhasMany

Attempts:

3 left

💡 Hint

Common Mistakes

Using belongsToMany instead of morphToMany breaks polymorphic many-to-many.

Using hasMany instead of morphToMany is incorrect for many-to-many polymorphic.

The morphToMany method defines a polymorphic many-to-many relation in the parent model, while morphTo accesses the parent in the related model.

5fill in blank

hard

Fill all three blanks to complete the polymorphic relation and query in Laravel.

Laravel

$comments = Comment::where('[1]_id', $post->id)
    ->where('[2]_type', get_class($post))
    ->get();

$post->[3]()->save(new Comment(['body' => 'Nice post!']));

Drag options to blanks, or click blank then click option'

Acommentable

Ccomments

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong column names breaks the query.

Using singular relation method name instead of plural causes errors.

Polymorphic relations use commentable_id and commentable_type columns to query related models. The relation method comments is used to save new comments.

Practice

1. What is the main purpose of polymorphic relationships in Laravel?

easy

A. To allow a model to belong to more than one other model on a single association

B. To create many-to-many relationships between two models

C. To enforce strict foreign key constraints in the database

D. To automatically generate database migrations

Solution

1. Step 1: Understand polymorphic relationships

   Polymorphic relationships allow a model to belong to multiple other models using a single association.

2. Step 2: Compare with other relationship types

   Unlike many-to-many or one-to-many, polymorphic lets one model relate to different models without separate foreign keys.

3. Final Answer:

   To allow a model to belong to more than one other model on a single association -> Option A

4. Quick Check:

   Polymorphic relationships = single association to multiple models [OK]

Hint: Polymorphic = one model relates to many different models [OK]

Common Mistakes:

• Confusing polymorphic with many-to-many relationships
• Thinking it automatically creates migrations
• Assuming it enforces database constraints

2. Which method should you use in the related model to define a polymorphic relationship?

easy

A. morphTo()

B. hasMany()

C. belongsToMany()

D. morphMany()

Solution

1. Step 1: Identify the related model method

   The related model uses morphTo() to define the polymorphic inverse relationship.

2. Step 2: Differentiate from owning model methods

   Owning models use morphMany(), but the related model uses morphTo().

3. Final Answer:

   morphTo() -> Option A

4. Quick Check:

   Related model uses morphTo() [OK]

Hint: Related model always uses morphTo() for polymorphic [OK]

Common Mistakes:

• Using morphMany() in the related model
• Confusing belongsToMany() with polymorphic
• Using hasMany() instead of morphTo()

3. Given the following code, what will $comment->commentable->name output?

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

$comment = Comment::find(1);

Assuming the comment belongs to a Post with name = 'Laravel Tips'.

medium

A. Error: Undefined property 'name'

B. 'Laravel Tips'

C. null

D. 'Comment'

Solution

1. Step 1: Understand morphTo() behavior

   The commentable() method returns the related model instance, here a Post.

2. Step 2: Access the related model's property

   Accessing name on the Post model returns 'Laravel Tips'.

3. Final Answer:

   'Laravel Tips' -> Option B

4. Quick Check:

   commentable->name = 'Laravel Tips' [OK]

Hint: morphTo() returns related model instance [OK]

Common Mistakes:

• Expecting null if not eager loaded
• Confusing property with method call
• Assuming error without checking model relation

4. What is wrong with this polymorphic relationship definition?

class Image extends Model {
  public function imageable() {
    return $this->morphMany();
  }
}

medium

A. morphMany() requires parameters but none are given

B. No relationship method is needed in Image model

C. The method name should be morphable()

D. The method should be morphTo(), not morphMany()

Solution

1. Step 1: Identify the model role

   Image is the related model, so it should use morphTo() for polymorphic inverse.

2. Step 2: Check method used

   morphMany() is for owning models, not related models.

3. Final Answer:

   The method should be morphTo(), not morphMany() -> Option D

4. Quick Check:

   Related model uses morphTo() [OK]

Hint: Related model must use morphTo(), not morphMany() [OK]

Common Mistakes:

• Using morphMany() without parameters
• Wrong method name for polymorphic inverse
• Thinking no method is needed

5. You want to create a polymorphic relationship where both Post and Video models can have many Comment models. Which of the following is the correct way to define the relationship in the Post model?

hard

A. public function comments() { return $this->belongsToMany(Comment::class); }

B. public function comments() { return $this->hasMany(Comment::class); }

C. public function comments() { return $this->morphMany(Comment::class, 'commentable'); }

D. public function comments() { return $this->morphTo(Comment::class, 'commentable'); }

Solution

1. Step 1: Identify owning model relationship

   Post owns many comments via polymorphic relation, so use morphMany().

2. Step 2: Use correct parameters

   morphMany() requires the related model class and the polymorphic name 'commentable'.

3. Final Answer:

   public function comments() { return $this->morphMany(Comment::class, 'commentable'); } -> Option C

4. Quick Check:

   Owning model uses morphMany() with polymorphic name [OK]

Hint: Owning model uses morphMany() with polymorphic name [OK]

Common Mistakes:

• Using hasMany() instead of morphMany()
• Using morphTo() in owning model
• Using belongsToMany() for polymorphic