Prestashop php formfield在选择下拉列表中设置值

I have a form created from php with FormField and i have the country field, which contains a list of countries. My question is how can i set a country to be selected, from php and not from html templates ( cause it's created as {form_field field=$field} in the tpl file ).

Here is my code:

$countries = Country::getCountries($this->context->language->id);
    $format['country'] = (new FormField)
        ->setName('country')
        ->setType('countrySelect')
        ->setLabel(
            $this->translator->trans(
                'Country', [], 'Shop.Forms.Labels'
            )
        )
        ->setRequired(true)
    ;

    foreach ($countries as $country) {
        $format['country']->addAvailableValue(
            $country['id_country'],
            $country['country']
        );
    }

If i could set it from php it would be awesome, cause i don't want to change core files or something. Thanks in advance.

(new FormField)->setValue ($value) should do the job, check out classes/form/FormField.php

public function setValue($value)