Replace Yii2 core class - yii2

Question

I am looking to override the default Model \yii\base\Model class with an extended version I have created. For arguments sake lets say I have it in backend\components\Model
I have tried putting both of these in the bootstrap config file but nothing changes - it continues to use the old class
Yii::$container->set('yii\base\Model', 'backend\components\Model');
Yii::$classMap['yii\base\Model'] = 'backend\components\Model';
and within the backend\Model file:
<?php
namespace backend\components;
use Yii;
use yii\base\InvalidConfigException;
use yii\base\UserException;
use yii\helpers\ArrayHelper;
class Model extends \yii\base\Model
{
/**
* Adds a new error to the specified attribute.
* #param string $attribute attribute name
* #param string $key attribute index
* #param string $error new error message
*/
public function addCustomError($attribute, $key, $error = '')
{
$this->_errors[$attribute][$key][] = $error;
}
}
I have also tried adding it to the config file using:
'container' => [
'definitions' => [
'yii\base\model'=>
['class'=>'backend\components\model']
]
],
No matter what I do - when I create a new ActiveRecord, it still holds the same yii\base\model class.
I have spent the better half of the afternoon trying to solve this and have gone through both the Yii documentation as well as the questions already on StackOverflow. There seems to be a recurring theme of the Container function not working and people transitioning to the ClassMap function - yet neither seem to work.
Thanks for the help.

Answer 1

Overriding by container works if you use container to instantiate overridden class (like Yii::$container->get('yii\base\Model');). If you have class MyModel extends \yii\base\Model you're NOT using container, yii\base\Model will be used as base class no matter what, because this is how PHP works and framework has no way to change that. If you want to do this you have at least 4 options:
Preferable: just use class MyModel extends \backend\components\Model for your models and avoid hacky class replacing.
Desperate 1: copy vendor/yiisoft/yii2/base/Model.php to overridden/Model.php, alter its source code, and override autoloading config to use overridden/Model.php for yii\base\Model - add:
Yii::$classMap['yii\base\Model'] = __DIR__ . '/../overridden/Model.php';
or
require __DIR__ . '/../overridden/Model.php';
after
require __DIR__ . '/../vendor/autoload.php';
require __DIR__ . '/../vendor/yiisoft/yii2/Yii.php
You need to sync all changes from vendor/yiisoft/yii2/base/Model.php to your copy after framework update. In general this should be last resort, since it is really easy to forget about it and get completely unexpected behavior.
Desperate 2: patch vendor/yiisoft/yii2/base/Model.php directly using cweagans/composer-patches. This is easier to maintain than second option, but it still may be surprising after some time. Also, at some point your patch may get conflicts after framework update and someone that knows what is happening will need to take a look at this.
Desperate 3: fork yiisoft/yii2 and do whatever you want - it is your framework now. It may be quite useful for large and active project, but in other case you may end up with completely outdated framework, because nobody cares to fetch changes from upstream.