Laravel - how to group by pivot table column - laravel

Question

I have a many to many relationship with one extra column in pivot table i.e module_id, i want to eager load the relationship data groupBy('module_id'). I tried couple of thing that didn't work, I successfully managed to get the desired structure but not through the eager loading (right way), i directly called the pivot table model queried the table. The problem is i cannot query pivot table directly becuase i have implemented the repository pattern.
This is how i queries the pivot directly.
$selectedGroups = RoleGroup::select('role_id', 'module_id', 'group_id')->where('role_id', $role->id)->get()->groupBy('module_id');
Migration:
Schema::create('role_groups', function (Blueprint $table)
{
$table->id();
$table->unsignedBigInteger('role_id');
$table->unsignedBigInteger('module_id');
$table->unsignedBigInteger('group_id');
$table->timestamps();
$table->foreign('role_id')->references('id')->on('roles')->onDelete('cascade');
$table->foreign('group_id')->references('id')->on('groups')->onDelete('cascade');
});
Role Model:
public function groups()
{
return $this->belongsToMany(Group::class, 'role_groups')->withPivot('module_id')->withTimestamps();
}
Group Model:
public function roles()
{
return $this->belongsToMany(Role::class, 'role_groups')->withPivot('module_id')->withTimestamps();
}
Desired Structre:
The keys are module_id and the values inside are group_id
{
"1": [
1
],
"2": [
1
],
"3": [
1
],
"4": [
1
],
"5": [
1,
2,
3,
4
]
}
What i got:
{
"1": [
{
"role_id": 1,
"module_id": 1,
"group_id": 1
},
{
"role_id": 1,
"module_id": 1,
"group_id": 3
}
],
"2": [
{
"role_id": 1,
"module_id": 2,
"group_id": 1
},
{
"role_id": 1,
"module_id": 2,
"group_id": 3
}
],
"3": [
{
"role_id": 1,
"module_id": 3,
"group_id": 1
}
],
"5": [
{
"role_id": 1,
"module_id": 5,
"group_id": 1
}
]
}

Answer 1

You may achieve this by grouping by multiple columns. i.e:
RoleGroup::query()
->select("module_id", "group_id")
->where("role_id", $role->id)
->groupBy("module_id", "group_id")
->get()
->reduce(
function (array $carry, Model $item) {
$carry[$item->module_id][] = $item->group_id;
return $carry;
}
, []);
References:
reduce()
groupBy()