In a many-to-many polymorphic relationship how do I set the "primary" key in the *ables table?

Due to privacy concerns I'm changing the names of my table but it goes something like this:

posts
    id - integer
    name - string

videos
    id - integer
    name - string

twowords
    id - integer
    name - string

twowordable
    twoword_id - integer
    twowordable_id - integer
    twowordable_type - string

I'm trying to save a relationship between a post and a twoword like this:

$post = App\Post::find(5);
$post->twowords()->attach($twowords_id);

And the error I get is:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'two_word_id' in 'field list' (SQL: insert into `twowordables` (`two_word_id`, `twowordable_id`, `twowordable_type`) values (59, 59, App\Tenant))

Where does laravel find the column name two_word_id? I want the column name to be twoword_id

michaeldyrynda

10 years ago

Level 41

You can pass the key name as the third parameter of the morphMany method, although, it's easiest to just stick to the default conventions unless you have a good reason otherwise.

The column name is derived from the eloquent model; which is why the conventions are in place.

1 like

zakiaziz

10 years ago

Level 3

In my post.php model file I have this:

    public function twowords()
    {
        return $this->morphToMany('App\TwoWords', 'twowordable', 'twoword_id');
    }

But still getting the same error

michaeldyrynda

10 years ago

Best Answer

Level 41

@zakiaziz now that I'm on a computer and not my phone, the method signature of morphToMany is as follows:

public function morphToMany($related, $name, $table = null, $foreignKey = null, $otherKey = null, $inverse = false)

If you take a look at Illuminate\Database\Eloquent\Model::morphToMany, you can see how this relationship is built up and why it expects a certain convention:

$table is derived as the plural of $name - twordables $foreignKey is derived as $name.'_id- twordable_id $otherKey is derived from (new $name)->getForeignKey(), which is the snake-cased class name with _id appended - two_word_id

So in your instance, you would (I'm pretty sure) need something along the following lines:

public function twowords()
{
    return $this->morphToMany(
        // the related model
        'App\TwoWords',
    
        // the relationship name
        'twowordable',
    
        // the table name, which would otherwise be derived from the relationship name - twowordables
        'twordable',

        // the foreign key will be twowordable_id, derived from the relationship name, which you're adhering to
        null,

        // the 'other' key, which would otherwise be derived from the related model's snake case name - two_word_id
        'twoword_id'
    );
}

4 likes

iatrodev

7 years ago

Level 3

Thank you for your reply! Exactly what i've been looking for

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