Laravel 5.2 Eloquent Relationships with Irregular Names - sql

Question

I'm building out my first project in Laravel and have run into a bit of a snag with a one to many relationship between two tables.
Historically, I would have done something like this in SQL to achieve my end goal:
SELECT tag_key.key
FROM tag
LEFT JOIN tag_key
ON tag.tag_key_id = tag_key.id;
With Laravel, I'm trying to do things the ORM way and am getting hung up, probably on a naming thing somewhere down the pipe. Here's the code:
Part 1: Migrations:
"tag_keys" table
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;
class CreateTagKeysTable extends Migration
{
/**
* Run the migrations.
*
* #return void
*/
public function up()
{
Schema::create('tag_keys', function (Blueprint $table) {
$table->increments('id');
$table->string('key', 128);
$table->timestamps();
});
}
/**
* Reverse the migrations.
*
* #return void
*/
public function down()
{
Schema::drop('tag_keys');
}
}
"tags" table
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;
class CreateTagsTable extends Migration
{
/**
* Run the migrations.
*
* #return void
*/
public function up()
{
Schema::create('tags', function (Blueprint $table) {
$table->increments('id');
$table->string('value', 128);
$table->integer('tag_key_id')->unsigned()->index();
$table->foreign('tag_key_id')->references('id')->on('tag_keys')->onDelete('cascade');
$table->timestamps();
});
}
/**
* Reverse the migrations.
*
* #return void
*/
public function down()
{
Schema::drop('tags');
}
}
Part 2: Models:
"TagKey" model
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class TagKey extends Model
{
protected $fillable = [
'key'
];
protected $dates = [];
protected $table = 'tag_keys';
/**
* Tag Keys have many Tags
*/
public function values()
{
return $this->hasMany('App\Tag');
}
}
"Tag" model
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Tag extends Model
{
protected $fillable = [
'value',
'tag_key_id'
];
protected $dates = [];
/**
* Tag values belong to Tag Keys
*/
public function key()
{
return $this->belongsTo('App\TagKey');
}
}
Independently, they both work just fine. However, when I jump into tinker and try this (given there is a valid row in both the "tag" and "tag_key" tables and given that id 1 in the "tag" has the value of 1 in the "tag_key" table under the "tag_key_id" column):
$tag = App\Tag::first();
$tag->key;
=> null
What am I missing here? How do I build this association?

Answer 1

When the foreign key name doesn't follow Eloquent conventions ("snake case" name of the owning model and suffix it with _id), you should specify it in the relationship:
TagKey object:
return $this->hasMany('App\Tag', 'tag_key_id');
Key object:
return $this->belongsTo('App\TagKey', 'tag_key_id');
More info in the documentation