public function rules()
    {
        return [
            [['formName'], 'required'],
            [['formName'], 'string', 'min' => 1, 'max' => 255, 'skipOnEmpty' => false]
        ];
    }

public function actionUpdate()
    {
        $this->requirePostRequest();
        $request = Craft::$app->getRequest();
        $site = Craft::$app->getSites()->getCurrentSite();

        $formName = $request->getBodyParam('formName');
        $formId = $request->getBodyParam('formId');

        // get ID (if exists)

        if ($formId) {
            $formRecord = FormRecord::find()
            ->where(['id'=>$formId])->one();
            // if count == null return false
        } else {
            $formRecord = new FormRecord;
        }

        $formRecord->formName = $formName;
        $formRecord->siteId = $site->id;
        if ($formRecord->validate()) {
        …