Show second & third model level - laravel

Question

I kow this is known subject discussed but I'm not getting the issue solved.
This is my current app model design:
Institution is the parent model of the app, which has many branches
Branch model has a polymorphic relationship with Building model (child enttity)
Classroom model belongs to Building model (1 Building, M Classroom)
I have a show.blade.php view where I list a Branch and I have 2 tabs for Buildings & Classrooms.
I can show each building for that branch but when I can' get to show all the classrooms in that branch (the relatioship is branch->building->classroom)
I have to solve this with a custom query in controller and then pass the result to the view or there is another approach?
Im trying to show classrooms from each institution ... but classrooms are related to builings.
$a=App\Institution::find(1); //OK
$a->branches; //OK
$a->buildings; //OK
$a->buildings->classrooms //Exception with message 'Property [classrooms] does not exist on this collection instance.
Regards
Institution Model
public function branches()
{
return $this->hasMany(Branch::class);
}
public function buildings()
{
return $this->morphMany('App\Building', 'buildingable');
}
Branch Model
public function institution()
{
return $this->belongsTo(Institution::class);
}
public function buildings()
{
return $this->morphMany('App\Building', 'buildingable');
}
Building Model
public function buildingable()
{
return $this->morphTo();
}
public function classrooms()
{
return $this->hasMany(Classroom::class);
}
Classroom Model
public function building()
{
return $this->belongsTo(Building::class);
}
TABLE STRUCTURES
public function up()
{
Schema::create('institutions', function (Blueprint $table) {
$table->increments('id');
$table->timestamps();
$table->string('inst_name', 30);
$table->string('inst_id_type', 10);
$table->string('inst_id_number', 10);
$table->string('inst_country', 15);
$table->string('inst_type', 15);
});
public function up()
{
Schema::create('branches', function (Blueprint $table) {
$table->increments('id');
$table->timestamps();
$table->string('branch_name', 30);
$table->string('branch_id_type', 10);
$table->string('branch_id_number', 10);
$table->string('branch_country', 15);
$table->string('branch_type', 15);
$table->integer('institution_id');
});
}
public function up()
{
Schema::create('buildings', function (Blueprint $table) {
$table->increments('id');
$table->timestamps();
$table->string('building_name', 30);
$table->integer('buildingable_id');
$table->string('buildingable_type');
});
}
public function up()
{
Schema::create('classrooms', function (Blueprint $table) {
$table->increments('id');
$table->timestamps();
$table->string('classroom_name', 20);
$table->integer('building_id');
$table->integer('employee_id');
});
}

Answer 1

$a->buildings->classrooms is the problem. $a->buildings is a collection, not an eloquent model. To get the classrooms of each building, you could use a foreach loop or the each() function on the connection.
foreach example:
foreach($a->buildings as $building) {
$classrooms = $building->classrooms;
// Do stuff here...
}
each() example:
$a->buildings->each(function ($building) {
$classrooms = $building->classrooms;
// Do stuff here...
}