Htydjtk

My questions:

1. 
   I want know how this works by each and every line of code


2. I want to add new attribute here


3. Difference between InstallData and InstallSchema

Here is InstallData.php

<?php

namespace vendorModuleSetup;



use MagentoCustomerModelCustomer;

use MagentoFrameworkSetupModuleContextInterface;

use MagentoFrameworkSetupModuleDataSetupInterface;



class InstallData implements MagentoFrameworkSetupInstallDataInterface

{

    private $eavSetupFactory;



    private $eavConfig;



    private $attributeResource;



    public function __construct(

        MagentoEavSetupEavSetupFactory $eavSetupFactory,

        MagentoEavModelConfig $eavConfig,

        MagentoCustomerModelResourceModelAttribute $attributeResource

    ) {

        $this->eavSetupFactory = $eavSetupFactory;

        $this->eavConfig = $eavConfig;

        $this->attributeResource = $attributeResource;

    }



    public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)

    {

        $eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);



        $eavSetup->removeAttribute(Customer::ENTITY, "skype");



        $attributeSetId = $eavSetup->getDefaultAttributeSetId(Customer::ENTITY);

        $attributeGroupId = $eavSetup->getDefaultAttributeGroupId(Customer::ENTITY);



        $eavSetup->addAttribute(Customer::ENTITY, 'skype', [

            // Attribute parameters

            'type' => 'varchar',

            'label' => 'Skype Account',

            'input' => 'text',

            'required' => true,

            'visible' => true,

            'user_defined' => true,

            'sort_order' => 990,

            'position' => 990,

            'system' => 0,

        ]);



        $attribute = $this->eavConfig->getAttribute(Customer::ENTITY, 'skype');

        $attribute->setData('attribute_set_id', $attributeSetId);

        $attribute->setData('attribute_group_id', $attributeGroupId);



        /*

        //You can use this attribute in the following forms

        adminhtml_checkout

        adminhtml_customer

        adminhtml_customer_address

        customer_account_create

        customer_account_edit

        customer_address_edit

        customer_register_address

        */



        $attribute->setData('used_in_forms', [

            'adminhtml_customer',

            'customer_account_create',

            'customer_account_edit'

        ]);



        $this->attributeResource->save($attribute);

    }

}

?>

First both InstallSchema And InstallData both method are called when you install any new module

Schema setup scripts change database schema, they create or change
needed database tables.
If module is installing, SetupInstallSchema::install() is executed.

It means it create new table and its fields with its structure.

InstallData setup scripts contain entries module needs to insert into
database.
Attributes that come with Magento by default,Cms pages, various default groups and roles, are all examples of data setup.

Data setup is executed after Schema setup, they function in a similar fashion.

So come to the conclustion, Main difference between both is InstallSchema is used to make table and its structure. While
InstallData is used to insert/add data into table.