Attaching a hasOne model to another Laravel/Eloquent model without specifying id

Question

Background

Given we have the following two tables where type_id references a row in questionType:

question

id | type_id | description
---+---------+------------
1  | 1       | A nice question
.. | ..      | ..

questionType

id | name 
---+----------------
1  | Multiple-choice 
.. | ..

with the following Eloquent models:

class Question extends Model {
    public function type() {
        return $this->hasOne( 'QuestionType', 'id', 'type_id' );
    }
}

class QuestionType extends Model {
}

Question 1

How can I add a new question that references an existing question type without manually doing anything with ids? For example the following works but is ugly imo since I have to manually assign the corresponding question type id:

$q = new Question;
$q->type_id = 1; // Multiple-choice
$q->description = 'This is a multiple-choice question';
$q->save();

One would think there was a way to let the ORM handle the id-assignment (isn't the point to avoid stuff like this with ORMs?), something along the lines of (this does not work in Eloquent ORM):

$q = new Question;
$q->type = QuestionType.where('name', '=', 'Multiple-choice');
$q->description = 'This is a multiple-choice question';
$q->save();

Question 2

In relation to question 1, how would I go about adding a new question that references a new question type without manually doing anything with ids? Similarly I imagine something along the lines of:

$t = new QuestionType;
$t->name = 'Another type';

$q = new Question;
$q->type = $t;
$q->description = 'This is a multiple-choice question';
$q->save();

Here I'd like $q->save() to save both the new question type and question (or something similar).

The following works, but again I'm assigning the id myself which I believe the ORM should handle:

$t = new QuestionType;
$t->name = 'Another type';
$t->save();

$q = new Question;
$q->type = $t->id;
$q->description = 'This is a multiple-choice question';
$q->save();

I've tried playing with different combinations of save(), update() methods without luck. I also looked for attach() which exists on the hasMany relationships but seem to be missing in hasOne.

Answer 1

First off, you misunderstood the relation you refer to.

Here's what you need:

// Question model
public function questionType()
{
  return $this->belongsTo('QuestionType', 'type_id');
}

// QuestionType model
public function questions()
{
  return $this->hasMany('Question', 'type_id');
}

then you can link them together like this:

$questionType = QuestionType::where(..)->first();

$question = new Question;
... // do something with it

// associate
$question->questionType()->associate($questionType);

// or the other way around - save new question and link to the type:
$questionType->questions()->save($question);

You can explicitly pass an id to associate as well:

$question->type_id = $someTypeId;
$question->save();

---

You can't do this:

$question->questionType = $someQuestionType;

for this way Eloquent handles model attributes, not relations.

---

Question 2:

$questionType = new QuestionType(['name' => 'multiple']);
$questionType->save();

$question = new Question([ ... some values ... ]);

// then either this way:
$questionType->questions()->save($question);

// or, again, the other way around:
$question->questionType()->associate($questionType);
$question->save();