Laravel save / update many to many relationship

by

tldr; Use sync with 2nd param false

Many-to-many relationship is belongsToMany on both models:

// Task model
public function users()
{
  return $this->belongsToMany('User', 'user_tasks'); // assuming user_id and task_id as fk
}

// User model
public function tasks()
{
  return $this->belongsToMany('Task', 'user_tasks');
}

In order to add new relation use attach or sync.

Difference between the two is:

1 attach will add new row on the pivot table without checking if it’s already there. It’s good when you have additional data linked to that relation, for example:

User and Exam linked with pivot table attempts: id, user_id, exam_id, score

I suppose this is not what you need in your situation:

$user->tasks()->getRelatedIds(); // [1,2,3,4,5,6]

$user->tasks()->attach([5,6,7]);
// then
$user->tasks()->getRelatedIds(); // [1,2,3,4,5,6,5,6,7]

2 sync on the other hand, will either remove all relations and set them up anew:

$user->tasks()->getRelatedIds(); // [1,2,3,4,5,6]

$user->tasks()->sync([1,2,3]);
// then
$user->tasks()->getRelatedIds(); // [1,2,3]

or it will setup new relations without detaching previous AND without adding duplicates:

$user->tasks()->sync([5,6,7,8], false); // 2nd param = detach
// then
$user->tasks()->getRelatedIds(); // [1,2,3,4,5,6,7,8]

More Related Contents:

  1. Laravel – Eloquent “Has”, “With”, “WhereHas” – What do they mean?
  2. Migration: Cannot add foreign key constraint
  3. Laravel Eloquent groupBy() AND also return count of each group
  4. Eloquent Collection: Counting and Detect Empty
  5. Eloquent eager load Order by
  6. Laravel. Use scope() in models with relation
  7. Laravel Eloquent “WHERE NOT IN”
  8. Laravel Eloquent – Attach vs Sync
  9. How to access model hasMany Relation with where condition?
  10. Eloquent push() and save() difference
  11. First Or Create
  12. Laravel: Returning the namespaced owner of a polymorphic relation
  13. Polymorphic Eloquent relationships with namespaces
  14. Clone an Eloquent object including all relationships?
  15. Laravel Check If Related Model Exists
  16. Laravel Eloquent vs DB facade: Why use Eloquent and decrease performance? [closed]
  17. How to Get the Current URL Inside @if Statement (Blade) in Laravel 4?
  18. Laravel Eloquent: How to order results of related models?
  19. Laravel – Forbidden You don’t have permission to access / on this server
  20. How to set a default attribute value for a Laravel / Eloquent model?
  21. How to use paginate() with a having() clause when column does not exist in table
  22. What is the difference between queue:work –daemon and queue:listen
  23. How to create a subquery using Laravel Eloquent?
  24. Eloquent model mass update
  25. Laravel: Get pivot data for specific many to many relation
  26. Find or Create with Eloquent
  27. Laravel: Change base URL?
  28. How to setup conditional relationship on Eloquent
  29. Laravel Many to many self referencing table only works one way
  30. Laravel Eloquent – Where In All

Leave a Comment