Possible to include getSObjectType() in for loop parameters?

Question

I'm wanting to build a for loop that can dynamically handle lists passed into a function for it.

Something along the lines of the following:

public static List<AggregateResult> aggregatePrep(List<sObject> records, Schema.DescribeFieldResult fieldToAggregate)
{
    List<AggregateResult> returnList = new List<AggregateResult>();
    Schema.SObjectType sot = records.getSObjectType();
    SObject sObj = sot.newSObject() ;
    SObjectField sf = fieldToAggregate.getSobjectField();

    for(Schema.SObjectType.getSObjectType(records) so : records)
    {
        returnList.add(so);
        //alternative to above is add(so.sf);
    }
    return returnList;
}

The issues I've run into are as follows:

1) using the for(Schema.SObjectType.getSObjectType(records) so : records) I return the error expecting an equals sign, found '(', so I suspect what I want may not be possible at all.

2) I try referencing sot directly as for(sot s : records) and it states invalid type: sot.

3) The alternative add of (so.sf); returns Field expression not allowed for generic SObject, which is why I would like to find a way to dynamically iterate through a list of matching type for records.

Is there any way to accomplish what I am trying to do? And if not, how should I handle this kind of situation, where I am trying to iterate through a list for items and add it to a different type of list?

Thanks!

Answer 1

AggregateResult can't be reliably created or modified. They're a construct for querying aggregate data from the database.

Instead, consider using a Map<Id, Object>:

public static Map<Id, Object> extractValues(SObject[] records, SObjectField field) {
  Map<Id, Object> results = new Map<Id, Object>();
  for(SObject record: records) {
    results.put(record.Id, record.get(field));
  }
  return results;
}

You can also build the map ahead of time to get specific subtypes:

public static void extract(Map<Id, Object> values, SObject[] source, SObjectField field) {
  for(SObject record: source) {
    values.put(record.Id, record.get(field));
  }
}

Which you can then do stuff with later:

Map<Id, Decimal> amounts = new Map<Id, Decimal>();
extract(amounts, [SELECT Amount FROM Opportunity], Opportunity.Amount);