Selecting a value from an n:n relationship - mysql

Question

I currently have three tables: users, roles, and a user_to_role “pivot” table defining a many-to-many relationship between users and roles:
users
protected $fillable = [
'name', 'email', 'password',
];
user_to_role
protected $fillable = [
'id', 'user_id', 'role_id'
];
roles
protected $fillable = [
'id', 'role_name',
];
The role_name values are admin and client.
When a user logs in, I want to show a view for the specific role that the user is assigned. I don't really know how to do that in the controller, however. I have something like the following, but I know it won’t work:
public function index()
{
if (Auth::user()->role_id==1) {
// and something here which I don't know
return view('homeadmin');
}
}
I know I have to take the id from the roles table, make the connection with the user_to_role pivot, and then join that with the users table, but I don't really know how.

Answer 1

You need to define a relationship between User model and Role model.
# User.php
public function roles()
{
return $this->belongsToMany(Role::class, 'user_to_role');
}
Optionally, define the relationship on Role model as well.
# Role.php
public function users()
{
return $this->belongsToMany(User::class, 'user_to_role');
}
Then, you can access the relationship and use collection methods on it.
public function index()
{
// or Auth::user()->roles->contains('role_name', 'admin') if you want to be specific
if (Auth::user()->roles->contains('id', 1)) {
return view('homeadmin');
}
return view('homeuser');
}
Optionally, you could make a method in the User model to check if an user is admin or client.
# User.php
public function isAdmin()
{
return $this->roles->contains('id', 1); // or contains('role_name', 'admin')
}
public function isClient()
{
return $this->roles->contains('id', 2); // or contains('role_name', 'client')
}
public function index()
{
if (Auth::user()->isAdmin()) {
return view('homeadmin');
}
return view('homeclient');
}
Eloquent Relationships - Many to Many
Collections - contains() method

Answer 2

First of all, if you have User and Role Model mapping to your users and roles table, the convention is to name your pivot table role_user. But you can get along with your current table naming as well.
I would agree the answer of IGP and add a few more suggestions.
If you just need to implement role and user and don't have to build it yourself, there are plenty of existing packages that can help you handle role-permission. You don't really needs to build from scratch. For example, depends on the Laravel version you use, you may choose;
spatie/laravel-permission
Bouncer
Zizaco/Entrust
If you would like to implement role management yourself, when you define your relationship, you need to think about if a user would have multiple roles in the future. Based on what you show us right now, there are only client and admin role. Looks like a user would only be either client or admin but not both. And if you are sure those are the only two roles and a user would be either one, you don't need to have roles table at all. You can just add a boolean column such as is_admin in users table to flag the role.
But let's say you will have more roles, and a user can have multiple roles at the same time. Then you DO need to define a many to many relationship. Other answers already provide example on that pretty well. I would also suggest to define a universal role-handling model function to check all roles. In your User.php model,
public function hasRole($role)
{
// check if user have any of the specified roles
if (is_array($role)) {
foreach($role as $r) {
if ($this->roles->contains('role_name', $r)) {
return true;
}
}
return false;
} else {
return $this->roles->contains('role_name', $role);
}
}
That way, in anywhere in your App, you can check your user role by calling
Auth::user()->hasRole('admin');
or check if user contains any role in a list by calling
Auth::user()->hasRole(['admin', 'client']);