Get Joomla Articles via Model inside static (Module) Method

Question

When calling an AJAX Method in a Module Helper file the method has to be static. I have no app context there, when doing the following:

public static function getDataAjax()
    {
        $data   = ExampleHelper::getJArticles();
        return $data;
    }

public static function getJArticles(){
        $app = Joomla\CMS\Factory::getApplication();
        $model = $app->bootComponent('com_content')->getMVCFactory()->createModel('Articles', 'Site', ['ignore_request' => true]);
        $articles = $model->getItems();
        return $articles;
}

An error 500 got thrown: Call to a member function get() on null

#0 /Users/MyUser/Sites/joomla5.site/libraries/src/MVC/Model/ListModel.php(222): Joomla\Component\Content\Site\Model\ArticlesModel->getListQuery()

#1/Users/MyUser/Sites/joomla5.site/libraries/src/MVC/Model/ListModel.php(271): Joomla\CMS\MVC\Model\ListModel->_getListQuery()

#2 /Users/MyUser/Sites/joomla5.site/components/com_content/src/Model/ArticlesModel.php(651)...

There is a similar question here (about getting articles in the backend) (Link) but as far as i can see the solution there does not help me.

I would like to use the model rather then doing my own database query here...

Edit: The AJAX call is done via com_ajax:

...
async loadData() {
        let requestString = this.prepareRequest();
        const res = await fetch(requestString);
        if (res.ok) {
            let parsed = await res.json();
            if (parsed.data && parsed.data.length > 0) {
                this.data = parsed.data;
            }
        }
        return this.data;
    }

    prepareRequest() {
        if (!this.checkConfiguration()) return;
        let requestString = 'index.php?option=com_ajax&module=' + this.moduleName + '&method=' + this.method + '&format=json';
        if (this.backendModule) {
            requestString = 'administrator/' + requestString;
        }
        requestString += '&limit=' + this.limit + '&page=' + this.page;
        return requestString;
    }

    checkConfiguration() {
        return !!(this.moduleName && this.method);
    }
...

Answer 1

As mentioned by Sharky i had to set the params state in de model. The feedback provided by Carlitorweb about the data that got send to the Ajax Method is also true (was not yet implemented). Working (full) example below:

public function getDataAjax()
    {
        $app = Factory::getApplication();
        $input       = $app->input;
        $preferences = array();
        $preferences['limit']        = $input->get('limit', 20, 'integer');
        $preferences['page']        = $input->get('page', 1, 'integer');

        $data   = ExampleHelper::getJArticles($app, $preferences);

        return $data;
    }

    private function getJArticles(SiteApplication $app, array $preferences = [])
    {
        $model = $app->bootComponent('com_content')->getMVCFactory()->createModel('Articles', 'Site', ['ignore_request' => true]);
        // Set the params state in the model
        $model->setState('params', clone ComponentHelper::getParams('com_content'));
        $model->setState('list.limit', $preferences['limit']);
        $model->setState('list.start', ($preferences['page'] - 1) * $preferences['limit']);
        $articles = $model->getItems();
        [...]
        return $articles;
}