Magento2 Unable to save custom category attribute

Question

I want a custom category attribute for my categories, so I have created a module with all the necessary files and code, in admin, I am able to see the custom field but when I am trying to save it the value doesn't save. For reference I am pasting my code, please suggest me where I am getting wrong or missing something.

/app/code/Belong/Categoryattrs/Setup/InstallData.php

namespace Belong\Categoryattrs\Setup;

use Magento\Framework\Setup\InstallDataInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Eav\Setup\EavSetupFactory;

class InstallData implements InstallDataInterface
{

private $eavSetupFactory;

public function __construct(EavSetupFactory $eavSetupFactory)
{
    $this->eavSetupFactory = $eavSetupFactory;
}

public function install(
    ModuleDataSetupInterface $setup,
    ModuleContextInterface $context
)
{
    $eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);

    $eavSetup->addAttribute(
        \Magento\Catalog\Model\Category::ENTITY,
        'alfasi_category_id',
        [
            'type'         => 'varchar',
            'label'        => 'Alfasi Category Id',
            'input'        => 'text',
            'sort_order'   => 100,
            'source'       => '',
            'global'       => 1,
            'visible'      => true,
            'required'     => false,
            'user_defined' => false,
            'default'      => null,
            'group'        => '',
            'backend'      => ''
        ]
    );
}

}

app/code/Belong/Categoryattrs/view/adminhtml/ui_component/category_form.xml

    <?xml version="1.0" ?>
    <form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
        <fieldset name="general">
            <field name="alfasi_category_id">
                <argument name="data" xsi:type="array">
                    <item name="config" xsi:type="array">
                        <item name="required" xsi:type="boolean">true</item>
                        <item name="validation" xsi:type="array">
                            <item name="required-entry" xsi:type="boolean">false</item>
                        </item>
                        <item name="sortOrder" xsi:type="number">333</item>
                        <item name="dataType" xsi:type="string">string</item>
                        <item name="formElement" xsi:type="string">input</item>
                        <item name="label" translate="true" xsi:type="string">Alfasi Category Id</item>
                    </item>
                </argument>
            </field>
        </fieldset>
    </form>

Answer 1

Please try below code:

app/code/Belong/Categoryattrs/Setup/InstallData.php

<?php

namespace Belong\Categoryattrs\Setup;

use Magento\Framework\Setup\InstallDataInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Catalog\Setup\CategorySetupFactory;

class InstallData
    implements InstallDataInterface
{
    /**
     * Category setup factory
     *
     * @var CategorySetupFactory
     */
    private $categorySetupFactory;

    /**
     * Init
     *
     * @param CategorySetupFactory $categorySetupFactory
     */
    public function __construct(
        CategorySetupFactory $categorySetupFactory
    ) {
        $this->categorySetupFactory = $categorySetupFactory;
    }

    /**
     * {@inheritdoc}
     */
    public function install(
        ModuleDataSetupInterface $setup,
        ModuleContextInterface $context
    ) {
        $setup->startSetup();

        /** @var \Magento\Catalog\Setup\CategorySetup $categorySetup */
        $categorySetup = $this->categorySetupFactory->create(['setup' => $setup]);

        $categorySetup->addAttribute(
            'catalog_category',
            'alfasi_category_id',
            [
                'type' => 'varchar',
                'label' => 'Alfasi Category Id',
                'input' => 'text',
                'required' => false,
                'sort_order' => 100,
                'global' => \Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface::SCOPE_STORE,
                'group' => 'General Information',
            ]
        );

        $setup->endSetup();
    }
}

app/code/Belong/Categoryattrs/view/adminhtml/ui_component/category_form.xml

<?xml version="1.0" encoding="UTF-8"?>

<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
    <fieldset name="alfasi_category_id">
        <argument name="data" xsi:type="array">
            <item name="config" xsi:type="array">
                <item name="label" xsi:type="string" translate="true">Additional Tab</item>
                <item name="collapsible" xsi:type="boolean">true</item>
                <item name="sortOrder" xsi:type="string">1000</item>
            </item>
        </argument>
        <field name="alfasi_category_id">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="dataType" xsi:type="string">string</item>
                    <item name="source" xsi:type="string">category</item>
                    <item name="label" xsi:type="string" translate="true">Alfasi Category Id</item>
                    <item name="visible" xsi:type="boolean">true</item>
                    <item name="required" xsi:type="boolean">false</item>
                    <item name="sortOrder" xsi:type="number">10</item>
                    <item name="validation" xsi:type="array">
                        <item name="required-entry" xsi:type="boolean">false</item>
                    </item>
                </item>
            </argument>
        </field>
    </fieldset>
</form>

Answer 2

    <?xml version="1.0" encoding="UTF-8"?>

    <form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
        <fieldset name="alfasi_category_id">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="label" xsi:type="string" translate="true">Additional Tab</item>
                    <item name="collapsible" xsi:type="boolean">true</item>
                    <item name="sortOrder" xsi:type="string">1000</item>
                </item>
            </argument>
            <field name="alfasi_category_id">
                <argument name="data" xsi:type="array">
                    <item name="config" xsi:type="array">
                        <item name="dataType" xsi:type="string">string</item>
                        <item name="source" xsi:type="string">category</item>
                        <item name="label" xsi:type="string" translate="true">Alfasi Category Id</item>
                        <item name="formElement" xsi:type="string">text</item>
                        <item name="visible" xsi:type="boolean">true</item>
                        <item name="required" xsi:type="boolean">false</item>
                        <item name="sortOrder" xsi:type="number">10</item>
                        <item name="validation" xsi:type="array">
                            <item name="required-entry" xsi:type="boolean">false</item>
                        </item>
                    </item>
                </argument>
            </field>
        </fieldset>
    </form> 

I added below code.

 <item name="formElement" xsi:type="string">text</item>