Eloquent relationships: cloumn doesn't exist - php

Question

I'm new to Laravel and am having a bit of a hard time cracking how relationships work. I'm building a simple e-commerce application, where each user has some orders, and order has one or many sub-orders, and each sub-order is linked to only one item (please don't comment on my scheme yet; for now I just need to figure out Eloquent and will be doing refactoring later :) ).
Following are my models:
class Order extends Model
{
//timestamp
protected $created_at;
public function sub_orders() {
return $this->hasMany('App\SubOrder');
}
public function user() {
return $this->belongsTo('App\User');
}
}
class SubOrder extends Model
{
protected $fillable = array('delivery_date', 'quantity', 'total_price', 'delivery_status');
public function item() {
return $this->hasOne('App\Item');
}
public function order() {
return $this->belongsTo('App\Order');
}
}
class Item extends Model
{
//note - slug is kind of categorization and is common to many items
protected $fillable = array('sku', 'name', 'slug', 'unit_price');
}
And here are the migrations:
class CreateOrdersTable extends Migration
{
/**
* Run the migrations.
*
* #return void
*/
public function up()
{
Schema::create('orders', function (Blueprint $table) {
$table->increments('id');
$table->timestamp('created_at');
//foreign keys
$table->unsignedInteger('user_id')->after('id');
$table->foreign('user_id')->references('id')->on('users') ->onDelete('cascade');
});
}
/**
* Reverse the migrations.
*
* #return void
*/
public function down()
{
Schema::dropIfExists('orders');
}
}
class CreateSubOrdersTable extends Migration
{
public function up()
{
Schema::create('sub_orders', function (Blueprint $table) {
$table->increments('id');
$table->date('delivery_date');
$table->decimal('quantity', 5, 2);
$table->decimal('total_price', 7, 2);
$table->enum('delivery_status', ['pending_from_farmer', 'ready_for_customer', 'out_for_delivery', 'delivered']);
//foreign keys
$table->unsignedInteger('order_id')->after('id');
$table->foreign('order_id')->references('id')->on('orders') ->onDelete('cascade');
$table->unsignedInteger('item_id')->after('order_id');
$table->foreign('item_id')->references('id')->on('items') ->onDelete('cascade');
});
}
public function down()
{
Schema::dropIfExists('sub_orders');
}
}
class CreateItemsTable extends Migration
{
public function up()
{
Schema::create('items', function (Blueprint $table) {
$table->increments('id');
$table->string('sku')->unique();
$table->string('name');
$table->string('slug');
$table->decimal('unit_price', 5, 2);
});
}
public function down()
{
Schema::dropIfExists('items');
}
}
The problematic expression is why I write App\Order::all()[0]->sub_orders[0]->item in my web.php and get the following error:
SQLSTATE[42703]: Undefined column: 7 ERROR: column items.sub_order_id does not exist
LINE 1: select * from "items" where "items"."sub_order_id" = $1 and ...
^ (SQL: select * from "items" where "items"."sub_order_id" = 1 and "items"."sub_order_id" is not null limit 1)
I don't understand why it's looking for sub_order_id in the items table. And what's the right way to go about doing it?

Answer 1

Overall: define the 1-to-1 relationship using hasOne or belongsTo will affect the target table where Laravel find the foreign key. hasOne assume there is a my_model_id in target table.And belongsTo assume there is a target_model_id in my table.
class SubOrder extends Model
{
public function item() {
return $this->hasOne('App\Item', 'id', 'item_id');
}
}
or
class SubOrder extends Model
{
public function item() {
return $this-> belongsTo('App\Item');
}
}
According to Laravel Doc
class User extends Model
{
/**
* Get the phone record associated with the user.
*/
public function phone()
{
return $this->hasOne('App\Phone');
}
}
Eloquent determines the foreign key of the relationship based on the model name. In the above case, the Phone model is automatically assumed to have a user_id foreign key. If you wish to override this convention, you may pass a second argument to the hasOne method:
$this->hasOne('App\Phone', 'foreign_key', 'local_key');
Or Defining The Inverse Of The Relationship
class Phone extends Model
{
/**
* Get the user that owns the phone.
*/
public function user()
{
return $this->belongsTo('App\User');
}
}
In the example above, Eloquent will try to match the user_id from the Phone model to an id on the User model.

Answer 2

Your SubOrder item has relationship of type OneToOne (hasOne is bidirectional) with an Item.
So Eloquent expects to have sub_order_id in the items table.
So the solution is to define the inverse of this relationship (belongsTo) in the Item model