Laravel three way polymorphic relation madness - php

Question

Laravel 7.0
I am trying to set up a system where users can belong to
different models, like Courses or Realms. I call this a
'membership'.
A user who is a member in a Realm or Course always has a
Role within that Realm, like 'amdin', 'editor', or 'guest'
I have models for User, Role, Memberable and the Course/Realm stuff.
Like this:
Role ⇦1:N⇦ Memberable ⇨N:1⇨ User
⇩
poly 1:1
⇩
Realm/Course/YouNameIt
At the moment I am using a wild mix of relations to get
more or less what I want. But my approach seems rather
gross to me, or even wrong.
For example, to get a list of models that I am a member of, I write:
User::find(2)->memberships()->get()
But this gives me a Collection of Memberables, not Realms or
Courses, which kind of sucks. Can this be remedied?
To get my first Realm/Course, I have to write:
User::find(2)->memberships()->first()->memberable // YUCK!
Here are my models:
class User {
public function memberships()
{
return $this->hasMany(Memberable::class)->with('memberable');
}
public function roles()
{
return $this->belongsToMany(Role::class, 'memberables')
->withPivot(['memberable_id', 'memberable_type']);
}
}
class Memberable extends Model
{
public function role()
{
return $this->hasOne(Role::class, 'id', 'role_id');
}
public function memberable()
{
return $this->morphTo('memberable');
}
}
trait HasMembers
{
public function members()
{
return $this->morphToMany(User::class, 'memberable', 'memberables')
->withPivot('role_id')
->join('roles', 'roles.id', 'memberables.role_id')
->addSelect(['role' => Role::select('name')
->whereColumn('role_id', 'roles.id')]);
}
}
class Realm extends Model
{
use HasMembers;
}
class Course extends Model
{
use HasMembers;
}
I know that questions like "is this good" or "is this bad" are difficult to answer, so I'll ask:
Is this so wrong that I should worry?
How could I improve this design?
I'll probably never have more Models that Realms and Courses that can have members. Is it smarter to ditch the whole memberable-polymorphism in favour of two separate tables? It IS nice to keep the flexibility the polymorphic approach offers.

Answer 1

You could just set up more relationships
User belongsToMany Roles
Roles belongsToMany Users
User morphedByMany Realm using Memberable
User morphedByMany Courses using Memberable
User morphedByMany YouNameIt using Memberable
Realm morphToMany User using Memberable
Courses morphToMany User using Memberable
YouNameIt morphToMany User using Memberable
I'd make Memberable a morph pivot.
class Memberable extends MorphPivot { ... }
With this, accessing the relationships isn't hard.
$user->roles // Get an Eloquent Collection made up from $user's roles.
$role->users // Get an Eloquent Collection made up from users that have $role.
$user->realms // Get an Eloquent Collection made up from $user's realms.
$user->courses // Get an Eloquent Collection made up from $user's courses.
$user->youNameIt // Get an Eloquent Collection made up from $user's youNameIt.
$realm->users // Get an Eloquent Collection made up from users associated with $realm.
$course->users // Get an Eloquent Collection made up from users associated with $course.
$youNameIt->users // Get an Eloquent Collection made up from users associated with $youNameIt.
And maybe make User <---> Roles relationship use a separate pivot. If not, then make it a morph relationship as well (User morphedByMany Role using Memberable, Role morphToMany User using Memberable)
The thing is, if you use a central table to morph everything up, it will grow a lot. You're essentially making it do the job of 3-4 pivots (in this example). If your data grows a lot, it might become a problem.
Also, different relationships might need different data from the pivot table but since you're only using a single table, that would complicate things unless you opt to use a json field.