model hasManyThrough relationship using a pivot model

Question

I have the following models/tables:

branch:
    id - integer

department:
    id - integer

teacher:
    id  - integer
    branch_department_id - integer

branch_department:
    id - integer
    branch_id - integer
    department_id - integer

• each branch has many departments through the pivot table branch_department
• each branch_department has many teachers

I want to model a hasManythrough relationship between branch and teachers

so from a specific branch i want to get all teachers through every branch_department that is related to that branch

How can I define this?

Answer 1

If you haven't define a BranchDepartment model.

class BranchDepartment extends Pivot
{
}

From here you can just define the hasManyThrough relationship on your Branch model.

public function teachers()
{
    return $this->hasManyThrough(
        Teacher::class,
        BranchDepartment::class,
        secondKey: 'branch_department_id',
    );
}