Retrieve data from many to many relationship in Laravel

I know the question has been responded many times, but for some reason I couldn’t make it work for my tables, no matter what, and I don’t understand why.

I’ve been trying this for like 4 hours and I couldn’t get it done right.

So here are my functions from two models:

ConducatorDoctorat

public function materii()
    {
        return $this->belongsToMany('AppDomeniuDoctorat', 'profesor_domeniu', 'domeniu_id', 'profesor_id');
    }

DomeniuDoctorat

public function materii()
    {
        return $this->belongsToMany('AppConducatorDoctorat', 'profesor_domeniu', 'profesor_id', 'domeniu_id');
    }

and profesor_domeniu schema:

<?php

use IlluminateDatabaseMigrationsMigration;
use IlluminateDatabaseSchemaBlueprint;
use IlluminateSupportFacadesSchema;

class ProfesorDomeniu extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('profesor_domeniu', function (Blueprint $table) {
            $table->unsignedBigInteger('profesor_id');
            $table->unsignedBigInteger('domeniu_id');
            
            $table->foreign('profesor_id')
                  ->references('id')->on('conducatori_doctorat')
                  ->onDelete('cascade');
            $table->foreign('domeniu_id')
                  ->references('id')->on('domenii_doctorat')
                  ->onDelete('cascade');
        });
    }

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

In my controller, I tried so many ways to do it, for example, like this:

public function edit($id)
    {
        $materii = ConducatorDoctorat::findOrFail($id)->materii()->pluck('domeniu_id');

        return view('admin.conducatori_doctorat.edit')->with([
            'materii' => $materii
        ]);
    }

but it still doesn’t work.

With the given $id, I want to retrieve all the data from profesor_domeniu where profesor_id == $id.
That’s all, but I can’t get it.

How can this be done and why doesn’t my approach work?

//edit for clarity:

conducator_doctorat is where the professors are stored and domenii_doctorat is where their fields are stored.

In profesor_domeniu, I store what each professor teaches, by linking an id from conducatori_doctorat to an id of a field from domenii_doctorat.

//edit2:

materii() means the fields they teach.

//edit3:

My many-to-many relationship with some data added into the pivot table profesor_domeniu.

Answers:

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Method 1

eager load your relationship on your model :

public function edit($id)
    {
        $conducatorDoctorat = ConducatorDoctorat::with('materii')->findOrFail($id);

       $materii = $conducatorDoctorat->materii;

        return view('admin.conducatori_doctorat.edit')->with([
            'materii' => $materii
        ]);
    }

you can also request only your materii related to your conducatorDoctorat :

public function edit($id)
    {
       

       $materii = DomeniuDoctorat::whereHas('materii', function($query) use ($id){
             $query->where('id', $id);
       })->get();

        return view('admin.conducatori_doctorat.edit')->with([
            'materii' => $materii
        ]);
    }

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0