<?php

namespace Pfay\Contacts\Setup;

use Magento\Framework\Setup\UpgradeSchemaInterface;
use Magento\Framework\Setup\SchemaSetupInterface;
use Magento\Framework\Setup\ModuleContextInterface;

class UpgradeSchema implements UpgradeSchemaInterface
{
    
    public function upgrade(SchemaSetupInterface $setup, ModuleContextInterface $context)
    {
        $setup->StartSetup();
        
        if(!$context->getVersion()){
            //no previous version found, installation, InstallSchema was just executed
            //be careful, since everything below is true for installation !
        }
        
        if(version_compare($context->getVersion(), '1.0.1') < 0){
            //code to upgrade to 1.0.1
        }
        
        if(version_compare($context->getVersion(), '1.0.3') < 0){
            //code to upgrade to 1.0.3
        }
        
        $setup->endSetup();
        
    }
    
}