How to use "Sync" from Laravel 5.1?

Question

I recently discovered a feature of eloquent called sync, I saw that he kind of compares the data passed with the data that’s in the database and deletes or inserts what’s different. I wanted to implement this in my application, but I didn’t understand how.

I have the following table:

id  id_setor_empresa  id_exame
1   5                 3
2   5                 20
3   5                 17

Which stores which exams should be done by employees of a sector.

Currently when an edition is made, I delete all the sector exams and register the new ones. How can I use the sync to do this more "clean"?

Answer 1

The method sync() is available since version 4, and is used only in many to many relations (belongsToMany).

This method is similar to attach(), follows explanation:

attach():

Used to add a new relation in the dynamic table.

Example:

$setor = Setor::find(5);
$setor->exames()->attach(2);

Your table would now look like this:

id  id_setor_empresa  id_exame
1   5                 3
2   5                 20
3   5                 17
4   5                 2

Sync():

Used to replace existing data with data reported via parameter.

Example:

$setor = Setor::find(5);
$setor->exames()->sync([20,10]);

Your table would now look like this:

id  id_setor_empresa  id_exame
2   5                 20
4   5                 10

In this case the data that is not in the array is deleted and inserts those that are not yet in the table.