Can anyone help me on how to save many to many relationship? I have tasks, user can have many tasks and task can have many users (many to many), What I want to achieve is that in update form admin can assign multiple users to specific task. This is done through html multiple select input
name="taskParticipants[]"
The catch here is that through the same form (input) you can add/remove users, that's why I have to use sync().
Maybe I should start from the beginning but don't know where to start...
This is my User model:
public function tasks()
{
return $this->belongsToMany('Task','user_tasks');
}
Task model
public function taskParticipants()
{
return $this->belongsToMany('User','user_tasks');
}
TaskController
public function update($task_id)
{
if (Input::has('taskParticipants'))
{
foreach(Input::get('taskParticipants') as $worker)
{
$task2 = $task->taskParticipants->toArray();
$task2 = array_add($task2,$task_id,$worker);
$task->taskParticipants()->sync(array($task2));
}
}
}
This is structure of tables
tasks
id|title|deadline
user_tasks
id|task_id|user_id
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]
Here's my notes on how to save and update on all the Eloquent relationships.
in One to One:
You have to use HasOne on the first model and BelongsTo on the second model
to add record on the first model (HasOne) use the save function
example: $post->comments()->save($comment);
to add record on the second model (BelongsTo) use the associate function
example: $user->account()->associate($account); $user->save();
in One to Many:
You have to use HasMany on the first model and BelongsTo on the second model
to add record on the first table (HasMany) use the save or saveMany functions
example: $post->comments()->saveMany($comments);
to add record on the second model (BelongsTo) use the associate function
example: $user->account()->associate($account); $user->save();
in Many to Many:
You have to use BelongsToMany on the first model and BelongsToMany on the second model
to add records on the pivot table use attach or sync functions
example: $user->roles()->attach($roleId);
in Polymorphic One to Many:
You have to use MorphMany on the main model and MorphTo on all the (***able) models
to add records on all the other models use the save
example: $course->tags()->save($tag);
the pivot table should have the following columns:
. main model ID
. (***able) ID
. (***able) Type
in Polymorphic Many to Many:
You have to use MorphByMany on the main model and MorphToMany on all the (***able) models
to add records on all the other models use the save or saveMany
example: $course->tags()->save($tag);
example: $course->tags()->saveMany([$tag_1, $tag_2, $tag_3]);
the pivot table should have the following columns:
. main model ID
. (***able) ID
. (***able) Type
in Has Many Through (shortcut):
You have to use HasManyThrough on the first table and have the normal relations on the other 2 tables
this doesn’t work for ManyToMany relationships (where there’s a pivot table)
however there’s a nice and easy solution just for that.
Here's an article I wrote, inspired by this answer. Important to check it: https://hackernoon.com/eloquent-relationships-cheat-sheet-5155498c209
syncWithoutDetaching([$id_one, $id_two, $id_three]); is what you are looking for. Actually it does the exact thing [sync with 2nd param false] does!
The sync function obliterates the exiting relationships and makes your array the entire list of relations. You want attach instead to add relations without removing others.
