Call to undefined method Illuminate\Database\Eloquent\Relations\BelongsTo::save() - laravel

Question

I want to insert data into multiple tables (one to one), but i get error and in my database the column "metode_id" is null. i want the "metode_id" is not null
this is class "Transaksi" :
class Transaksi extends Model
{
protected $table = "transaksi";
protected $primarykey = "id";
protected $fillable = ['stok_kedelai', 'stok_ragi', 'harga_kedelai', 'harga_ragi'];
public function metode()
{
return $this->belongsTo('App\Metode');
}
public function pengguna()
{
return $this->belongsTo('App\Pengguna');
}
}
This is class "Metode" :
class Metode extends Model
{
protected $table = "metode";
protected $primarykey = "id";
protected $fillable = ['bni', 'bri', 'mandiri', 'bca', 'btpn', 'ovo', 'gopay', 'dana'];
public function transaksi()
{
return $this->hasOne('App\Transaksi', 'metode_id');
}
}
This is database of "Transaksi" :
public function up()
{
Schema::create('transaksi', function (Blueprint $table) {
$table->bigIncrements('id');
$table->bigInteger('pengguna_id')->unsigned();
$table->integer('stok_kedelai');
$table->integer('stok_ragi');
$table->integer('harga_kedelai');
$table->integer('harga_ragi');
$table->bigInteger('metode_id')->unsigned();
$table->timestamps();
});
Schema::table('transaksi', function (Blueprint $table) {
$table->foreign('pengguna_id')->references('id')->on('pengguna')->onDelete('cascade')->onUpdate('cascade');
});
Schema::table('transaksi', function (Blueprint $table) {
$table->foreign('metode_id')->references('id')->on('metode')->onDelete('cascade')->onUpdate('cascade');
});
}
This is database of "Metode" :
public function up()
{
Schema::create('metode', function (Blueprint $table) {
$table->bigIncrements('id');
$table->integer('bni')->nullable();
$table->integer('bri')->nullable();
$table->integer('mandiri')->nullable();
$table->integer('bca')->nullable();
$table->integer('btpn')->nullable();
$table->integer('ovo')->nullable();
$table->integer('gopay')->nullable();
$table->integer('dana')->nullable();
$table->timestamps();
});
}
i want insert data into mutiple table that which depends on the "id" of pengguna table but i get error Call to undefined method Illuminate\Database\Eloquent\Relations\BelongsTo::save()
public function data_penjualan(Request $request)
{
$pengguna = Pengguna::where('id', Auth::user()->id)->first();
$transaksi = new Transaksi();
$transaksi->stok_kedelai = $request->stok_kedelai;
$transaksi->stok_ragi = $request->stok_ragi;
$transaksi->harga_kedelai = $request->harga_kedelai;
$transaksi->harga_ragi = $request->harga_ragi;
$pengguna->transaksi()->save($transaksi);
$metode = new Metode();
$metode->bni = $request->bni;
$transaksi->metode()->save($metode);
return view('transaksi.supplier', compact('transaksi'));
}
this is my database, the "metode_id" get null, how i want that "metode_id" is not null :
enter image description here

Answer 1

If you try to update a belongsTo relationship, you have to use the associate method instead of save method.
...
$metode = new Metode();
$metode->bni = $request->bni;
$metode->save();
$transaksi->metode()->associate($metode);
$transaksi->save();
...

Answer 2

If you try to SaveMethod in the belongsTo relationship.
Add Comment(controller file)
public function addComment($id)
{
$comment = new Comment(['comment' =>'Comment 1']);
$user = User::find(1);
$user->comment()->save($comment);
return "Comment Submitted";
}
Comment.php (Model File)
class Comment extends Model
{
use HasFactory;
protected $table ="comments";
protected $fillable = ['comment'];
public function User()
{
return $this->belongsTo(User::class);
}
}
web.php (Route File)
Route::get('comment/{id}',[UserController::class,'addComment']);