Laravel：在多对多关系上添加约束

Question

Consider this simple many-to-many relationship in Laravel:

class User extends Eloquent {
    public function roles()
    {
        return $this->belongsToMany('Role');
    }
}

and

class Role extends Eloquent {
    public function users()
    {
        return $this->belongsToMany('User');
    }
}

This is ok with schema of role_user that keeps user_id and role_id. But what we if have some other constraints? For example in an app like Github, user is admin in repository A and is regular user in repository B. So we add repository_id to role_user table, but when I want to query user->roles I want to look for that in current repository, that I keep reference of current_repository_id in session. What changes should I do in models to do that?

---

Note: I don't want to change anything in using-code! Isn't anyway to put filter logic in model declaration? Because I'm at the middle of big project and it's tough to change every usage. Is it possible?

Answer 1

//User model 
public function roles()
{
    $repoID = MyApp::currentRepoID();

    return $this->belongsToMany('Role', 'pivot_table_name', 'user_id', 'role_id')
        ->wherePivot('repository_id', $repoID);
}