src/widgets/LocationFormWidget.php
protected function city()
    {
        $pluginOptions = [
            'url' => Url::to(["/{$this->module->id}/city/list"])
            , 'depends' => [$this->fieldIds['country']]
        ];
        if (isset($this->fieldIds['state'])) {
            $pluginOptions['depends'][] = $this->fieldIds['state'];
            $pluginOptions['initDepends'] = [$this->fieldIds['country']];
        } else {
            $pluginOptions['depends'][] = null;
        }

        if (isset($this->fieldIds['region'])) {
            $pluginOptions['depends'][] = $this->fieldIds['region'];
            if (isset($this->fieldIds['state'])) {
                $pluginOptions['initDepends'][] = $this->fieldIds['state'];
            }
        } else {
            $pluginOptions['depends'][] = null;
        }

        $this->parts['{city}'] = $this->form->field($this->model, $this->model->getCityPropertyName())->widget(DepDrop::className(), [
            'options' => [
                'id' => $this->fieldIds['city']
                , 'cityholder' => Yii::t('jlorente/location', 'Select city')
                , 'name' => $this->getSubmitModelName($this->model->getCityPropertyName())
            ]
            , 'data' => ArrayHelper::map(City::find()->where(['region_id' => $this->model->region_id])->orderBy(['name' => SORT_ASC])->all(), 'id', 'name')
            , 'pluginOptions' => $pluginOptions
        ]);
    }
protected function city()
    {
        $pluginOptions = [
            'url' => Url::to(["/{$this->module->id}/city/list"])
            , 'depends' => [$this->fieldIds['country']]
        ];
        if (isset($this->fieldIds['state'])) {
            $pluginOptions['depends'][] = $this->fieldIds['state'];
            $pluginOptions['initDepends'] = [$this->fieldIds['country']];
        } else {
            $pluginOptions['depends'][] = null;
        }

        if (isset($this->fieldIds['region'])) {
            $pluginOptions['depends'][] = $this->fieldIds['region'];
            if (isset($this->fieldIds['state'])) {
                $pluginOptions['initDepends'][] = $this->fieldIds['state'];
            }
        } else {
            $pluginOptions['depends'][] = null;
        }

        $this->parts['{city}'] = $this->form->field($this->model, $this->model->getCityPropertyName())->widget(DepDrop::className(), [
            'options' => [
                'id' => $this->fieldIds['city']
                , 'cityholder' => Yii::t('jlorente/location', 'Select city')
                , 'name' => $this->getSubmitModelName($this->model->getCityPropertyName())
            ]
            , 'data' => ArrayHelper::map(City::find()->where(['region_id' => $this->model->region_id])->orderBy(['name' => SORT_ASC])->all(), 'id', 'name')
            , 'pluginOptions' => $pluginOptions
        ]);
    }
Renders the city part.