Yii2 RESTful relational data - rest

Question

I am having some trouble getting the Yii2 RESTful API returning relational data. I have this working when viewed through the frontend but i am trying to get the same data through the API and its not working the same way.
Tables
country - PK is population_id
population - Foreign Key is country.population_id
I am getting this error:
{ "success": false, "data": { "name": "Invalid Configuration",
"message": "The \"query\" property must be an instance of a class that
implements the QueryInterface e.g. yii\db\Query or its subclasses.",
"code": 0, "type": "yii\base\InvalidConfigException", "file":
"C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\data\ActiveDataProvider.php",
"line": 100, "stack-trace": [ "#0
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\data\BaseDataProvider.php(79):
yii\data\ActiveDataProvider->prepareModels()", "#1
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\data\BaseDataProvider.php(92):
yii\data\BaseDataProvider->prepare()", "#2
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\rest\Serializer.php(162):
yii\data\BaseDataProvider->getModels()", "#3
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\rest\Serializer.php(131):
yii\rest\Serializer->serializeDataProvider(Object(yii\data\ActiveDataProvider))",
"#4
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\rest\Controller.php(97):
yii\rest\Serializer->serialize(Object(yii\data\ActiveDataProvider))",
"#5
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\rest\Controller.php(75):
yii\rest\Controller->serializeData(Object(yii\data\ActiveDataProvider))",
"#6
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\base\Controller.php(153):
yii\rest\Controller->afterAction(Object(yii\base\InlineAction),
Object(yii\data\ActiveDataProvider))", "#7
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\base\Module.php(455):
yii\base\Controller->runAction('index', Array)", "#8
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\web\Application.php(83):
yii\base\Module->runAction('v1/country/inde...', Array)", "#9
C:\xampp\htdocs\AdvancedAPI\vendor\yiisoft\yii2\base\Application.php(375):
yii\web\Application->handleRequest(Object(yii\web\Request))", "#10
C:\xampp\htdocs\AdvancedAPI\api\web\index.php(17):
yii\base\Application->run()", "#11 {main}" ] } }
model (Country.php):
<?php
namespace api\modules\v1\models;
use \yii\db\ActiveRecord;
class Country extends ActiveRecord
{
public static function tableName()
{
return 'country';
}
public function getCountries()
{
//return $this->hasMany(Population::className(), ['population_id' => 'population_id']);
return $this->hasMany(Country::className(), ['population_id' => 'population_id']);
}
public function getPopulationNumber()
{
//return $this->hasOne(Country::className(), ['population_id' => 'population_id']);
return $this->hasOne(Population::className(), ['population_id' => 'population_id']);
}
}
model (Population.php):
<?php
namespace api\modules\v1\models;
use \yii\db\ActiveRecord;
class Population extends ActiveRecord
{
/**
* #inheritdoc
*/
public static function tableName()
{
return 'population';
}
/**
* #inheritdoc
*/
public static function primaryKey()
{
return ['p_id'];
}
}
controller (CountryController.php):
<?php
namespace api\modules\v1\controllers;
use yii\rest\Controller;
use yii\data\ActiveDataProvider;
use api\modules\v1\models\Country;
class CountryController extends Controller
{
public function actionIndex()
{
$query = Country::find()->with('countries', 'populationNumber')->all();
//$query = Country::find();
return new ActiveDataProvider([
'query' => $query,
]);
}
}

Answer 1

You need to remove all() part from your query. So the code should be:
<?php
namespace api\modules\v1\controllers;
use yii\rest\Controller;
use yii\data\ActiveDataProvider;
use api\modules\v1\models\Country;
class CountryController extends Controller
{
public function actionIndex()
{
$query = Country::find()->with('countries', 'populationNumber');
//$query = Country::find();
return new ActiveDataProvider([
'query' => $query,
]);
}
}