NULL value on attach()

$this->belongsToMany should only be used when you have a pivot table.

For this a Student belongs to many schools and school belongs to many Student

can you show your migrations for the three tables?

Hi Snapey - Thanks. I am using a school_student (school_id, student_user_id) pivot table. Here are the migrations:

class CreateSchoolsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('schools', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->string('address_01');
            $table->string('address_02');
            $table->string('city');
            $table->integer('geo_states_id');
            $table->string('postal_code');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('schools');
    }
}

class CreateStudentsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('students', function (Blueprint $table) {
            $table->unsignedBigInteger('user_id')->primary()
                    ->foreign('user_id')->references('id')->on('users')
                    ->onDelete('cascade');
            $table->integer('class_of');
            $table->integer('height')->default(30);
            $table->datetime('birthday')->nullable();
            $table->integer('shirt_size')->default(1)
                    ->foreign('shirt_size')->references('id')->on('shirt_sizes')
                    ->onDelete('cascade'); //Medium
            $table->integer('updated_by')->default(-1);
            $table->timestamps();
            $table->softDeletes();
            
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('students');
    }
}

class SchoolStudent extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::dropIfExists('school_student');
        
        Schema::create('school_student', function (Blueprint $table) {
            $table->unsignedBigInteger('school_id'); //user_id
            $table->unsignedBigInteger('student_user_id'); //user_id
            $table->unique(['school_id, student_user_id']);
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('school_student');
    }
}

Thanks for any additional help!

You are not using incrementing ID on your students?

you should have public $incrementing=false; on your model?

Hi Snapey - In my implementation are also users and Student is an extension of the User() model. I set the user_id as the primary key (i.e. protected $primaryKey = 'user_id' in Student()), which increments.

did you try my suggestion?

👋 Hi there !

I think the problem is that you updated the default primaryKey property on you Student model.

protected $primaryKey = 'user_id';

However, Laravel uses that property to define which column name to use with relationships. Meaning when trying to attach the school to the student, it tries to store the user_id property of the Student model in the student_user_id column of you pivot table. But you stored the authenticated user's id inside the id property of the Student meaning you user_id property is null. At least that's my understanding of it.

$student = new Student();
$student->user_id = auth()->user()->id;

Hope it helps ! 🤞

Hi Snapey - I replied to your questions regarding the pivot table, migrations and incrementing ID, but don't see any suggestions. Am I missing something here?

Thanks Nicolas - So using your analysis and Snapey's, does this suggest that I:

1. Setting an independent id for the Student() model and
2. Include a foreign key reference to the user_id?

@rretzko You are creating/ newing up student and school models, but you don't save them to the database.

I would:

1. Find or Create School, when created save it.
2. Find or Create Student, and associate it with the School and save.

You have this in your User model

    public function schools()
    {
        return $this->belongsToMany(School::class,'school_student','school_id', 'student_user_id');
    }

and this in your Student model

    public function schools()
    {
        return $this->belongsToMany(School::class);
    }

not tested but imo you should specify the keys for the relation as you do in your user model.

EDIT : Or maybe

public function store(\App\Http\Requests\StudentAddSchoolStoreRequest $request)
    {
        $student = new Student();
	// Replace id with user_id
        $student->user_id = auth()->user()->id;
        $school = new School();
  
        $school->id = $request->id;
        $student->schools()->attach($request->id);

        return redirect('school')->with('message', 'Successful update!');
    }

Thanks Stereoh. My Users are teachers, students and parents, so the implementation of schools dependent on student_user_id in the User model won't work for my implementation. HOWEVER, when i edited the store() function to $student->student_user_id = auth()->user()->id; , this worked. I need to pull this apart to understand the 'why' , but thanks to all for the guidance!