Laravel：对多对多关系添加约束

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);
}

Answer 2

If you need to add additional fields to the pivot table, you should use ->withPivot() method. If your pivot table structure is like:

id | role_id | user_id | repository_id

you should use

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

Then, wherever you use it, you have to do:

$role = Role::find(1);
$role->pivot->repository_id;

or

$user = User::find(1);
foreach ($user->roles as $role) {
    echo $role->pivot->repository_id;
}

Answer 3

Check out Eloquent Triple Pivot (also on Packagist), it sounds like it does exactly what you want.

You'd set up your Models as User , Repository and Role (a User has many Repository s and can have a Role in each). Then look at the docs on the Github page (particularly step 6), and you'd define this on your Repository model:

class Repository extends Eloquent {
    ...
    public function getRolesAttribute() {
        return $this->getThirdAttribute();
    }
}

Then you can simply call

$user = User::find(1);

$repo = $user->repositories->first();
// or
$repo = $user->repositories->find(73);

$roles = $repo->roles;

// Or the above can be condensed into just...
$roles = User::findOrFail( 1 )
             ->repositories()
             ->findOrFail( 73 )
             ->roles;