global class CustomerCunit
{
    global static String createNewAccount(list<accountWrapper> accwrapList) 
    {
        //RestRequest req = RestContext.request;
        //RestResponse res = RestContext.response;
        string returnString='';
        try
        {
			list<account> acclist = new list<account>();
        
            system.debug('*****' + accwrapList);
            for(accountWrapper wrap : accwrapList) 
            {
				Account acc = new Account();
				acc.Name= wrap.AccName;
				acc.Potential_Installations__c =wrap.PotentialInstallations;
				acclist.add(acc);
				acc.Customer_Segment_Lookup__c=wrap.CustomerSegmentLookup;
			}
            
            if (acclist.size() > 0)
            {
				insert acclist;
				
				//Note: SIze of accList and accwrapList will be same and order of record in list will be same as well so iterate on the size of any one list doesn't matter
				list<Cable_unit__c> Cunitlist= new list<Cable_unit__c>();
				for(Integer index = 0; index < accwrapList.size(); index++) {
					Cable_Unit__c Cunit= new  Cable_Unit__c();
					Cunit.Municipaly__c =wrap.Municipaly;
					Cunit.Housing_Type__c=wrap.HousingTypeLookup;
					Cunit.Housing_Ownership__c=wrap.HousingOwnershipLookup;
					Cunit.Cable_Unit_post_Code__c= wrap.CableUnitPostCode;
					Cunit.Building_Type__c=wrap.BuildingType;
					Cunit.Cable_Unit_No__c=wrap.CableUnitNo;
					Cunit.Account__c = acclist[index].Id;		//Here building relationship between Account(Parent) and Cable_Unit__c(Child). You can give Cunit.Account__c this api name according to you.
					CunitList.add(Cunit);
				}
				insert CunitList;
				returnString='Successful';
            }
            else
            {
				returnString='Failed';
            }        
        }
        catch(exception ex)
        {
            returnString = 'Request got failed: Error details-'+ex.getmessage();
        }
        return returnString;
    }
    
    
    global class accountWrapper
    {
		global string AccName;
		global Integer PotentialInstallations;
		global string Municipaly;
		global string CustomerSegmentLookup;
		global string HousingTypeLookup;
		global string HousingOwnershipLookup;
		global string CableUnitPostCode;
		global string CableUnitNo;
		global string BuildingType;
    }
}