Accessing Parent Field Values from sObjects in Dynamic Queries Using Dynamic Apex

sObjectScript.apxc

//------------Accessing parent field values in child to parent dynamic query----
//Below is static method which can be used to fetch field values.
//You need to pass sObject and fieldAPIName to get field value
public static string ExtractFieldValues(sObject sb, string fieldAPIName){
	string fvalue='';
	if(fieldAPIName.contains('.')){
		List<string> splitedFields = fieldAPIName.split('\\.');
		try{
			for(integer i=0;i<splitedFields.size()-1;i++){
				sb=sb.getSobject(splitedFields[i]);   
			}
			fvalue = string.valueof(sb.get(splitedFields[splitedFields.size()-1]));
		}catch(exception ex){
		   system.debug('******exception while fetching fieldValues as relationship '+fieldAPIName+'  value is blank.'+ex.getmessage()); 
		   fvalue='';
		}
		
	}else if(sb.get(fieldAPIName)!=null){
		fvalue = string.valueOf(sb.get(fieldAPIName));
	}
	return fvalue;
}

List<string> fieldAPINamesList = new List<string>{'Id','Opportunity.Name','Opportunity.Partner__r.Name','Product2.Name'};
string qString ='Select '+string.join(fieldAPINamesList,',')+ ' from OpportunityLineItem where id=\'00k90000002z4ml\'';
system.debug('****qString:'+qString);
sobject sb = database.query(qString);
//syntax to get OpportunityLineItem Id  value from sObject
string OpportunityLineItemId = string.valueof(sb.get('Id'));
system.debug('******OpportunityLineItemId:'+OpportunityLineItemId);
//syntax to get Opportunity.Name field value from sObject
string OpportunityName = string.valueof(sb.getSobject('Opportunity').get('Name'));
system.debug('******OpportunityName:'+OpportunityName);
//syntax to get Opportunity.Partner__r.Name field value from sObject
//If partner field in opportunity is blank then you will get null pointer exception
string partnerName = string.valueof(sb.getSobject('Opportunity').getSObject('Partner__r').get('Name'));
system.debug('******partnerName:'+partnerName);

//Note: While accessing the parent record details in child to parent query, you will get null pointer exception if parent is blank in child record.

//Below is sample code to get field values by using utility method defined above
for(string fieldName : fieldAPINamesList){
	string fieldvalue = ExtractFieldValues(sb,fieldName);
	system.debug('******fieldvalue using utility method:'+fieldvalue);
}