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.

Solution

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();

Comments

[olerass]

Regarding question 1: the second method is pseudocode, it does not work in Laravel (Eloquent ORM). Or at least, I do not know how to do it. Do you? Regarding question 2: you are connecting Question to $t at $q->type = $t, so I'm not sure I understand your concern about what the ORM should decide. Of course it should save $t and $q at $q->save(), and if you do not connect $t2 to anything or save it manually it is not saved.

[olerass]

Thanks so much Jarek! It seems I had mixed up the semantics of hasOne and belongsTo. In my mind $this->hasOne('QuestionType') where $this is a Question means that Question has a QuestionType. After all that's what it implies when you real it aloud right?. But apparently it's the other way around -- confusing!

[Jarek Tkaczyk]

@olerass It might be misleading in the beginning. But think about it - does really a question have a type? No, it rather belongs to a type and that's what Eloquent implies.

[Andrew Mast]

I know this is an old thread, but I have a solution where you can directly set the question type with $question->questionType = $someQuestionType;. Code: Pastebin

[Stanley Aloh]

This helped me overcome a problem I had with user having one roles in my laravel application