While trying to get relational value system console generates exception

Question

I am getting

"Line: 24, Column: 1 System.SObjectException: SObject row was retrieved via SOQL without querying the requested field: Account.Contact__r"

Here is my Code can you please help me out to find relational object's field value

String sTemp = 'Contact__r.CreatedBy.profileid';
public String getAllQuery {get;set;}
List<Schema.SObjectField> tempFields;
public Id oid = '00128000003P6nL';
public SObject resultObject {get;set;}
public List<Schema.DescribeFieldResult> fields {get;set;}
public static final String ERROR_ID_MISSING = 'There was no id passed in the parameters. Id is required.';
public static final String QUERY_SELECT = 'select ';
public static final String QUERY_FROM = ' from ';
public static final String QUERY_WHERE = ' where Id = \'';
fields = new List<Schema.DescribeFieldResult>();
Schema.DescribeSObjectResult objDescribe = oid.getSObjectType().getDescribe();
  Map<String, Schema.SObjectField> fieldMap = objDescribe.fields.getMap();
  tempFields = fieldMap.values();
  for(Schema.SObjectField sof : tempFields){
    fields.add(sof.getDescribe());
  }
  getAllQuery = buildQueryAllString(fields,objDescribe,oid);
  resultObject = Database.query(getAllQuery);
  if(sTemp.contains('.')){
    String[] arrTest = sTemp.split('\\.');
    String sRelatedValue = '';
    sObject tempObject ;
    tempObject = (SObject)resultObject.getSObject(arrTest[0]);
  }
public String buildQueryAllString(List<Schema.DescribeFieldResult> queryFields,DescribeSObjectResult obj, String theId){
  String query = QUERY_SELECT;
  for(Schema.DescribeFieldResult dfr : queryFields)
  {
      query = query + dfr.getName() + ',';
  }
  query = query.subString(0,query.length() - 1);
  query = query + QUERY_FROM;
  query = query + obj.getName();
  query = query + QUERY_WHERE;
  query = query + theId + '\'';
  system.debug('Build Query == ' + query);
  return query;
}

Answer 1

It looks like you have built a function to query all of the fields on a particular object - Account in this case, base on the value stored in oid.

After performing that query, you are trying to retrieve the value of the field named: Contact__r. This is where the error occurs. There is no field named Contact__r (or profileid for that matter) on the Account object.

Even if you left the sTemp string intact instead of splitting it, you would still run into this same type of error because buildQueryAllString only queries fields on one object, and doesn't query fields on related objects.

In your sTemp string, Contact__r.CreatedBy.profileid, you are traversing two relationships. You go from the Account to a Contact to a User; It is the User object where the profileid is actually located.

Answer 2

As @martin has pointed out you are missing the child relations in your query and trying to access them in your results set.
Use getChildRelationShips() on your objDescribe instance and collect the required child fields as well to pass into the query. ChildRelationShip Class also may helpful for you.