[SalesForce] Comparing Two Lists of Related Objects

I have two custom objects, Question__c and Response__c. There is a lookup field named Related_Question__c on the Response__c object to relate the two. In my VF controller I have two Lists, one for each object. My objective is to find all records in the Question List that do not have a match in the Response List (ie questions that haven't been answered yet).

I believe I need to use a map for this but am unsure of exactly how to accomplish this. Any advice would be appreciated. Thanks in advance.

Here's what I have so far to build the two Lists:

List <Question__c> questions = [select Id, Name From Question__c];
List <Response__c> questionResponses = [select Id, Name, Related_Question__c From Response__c Where Related_Question__c IN: questions};

Best Answer

Can you try something like this ?

List<Id> l = new List<Id>();
Map<Id,Response__c> qr = new Map<Id,Response__c>();
for(Response__c r : questionResponses)
{

    qr.put(r.Related_Question__r.Id,r);
}
for(Question__c q :  questions)
{

  if(qr.get(q.Id) == null)
 {
      l.add(q.Id);    
}

}
System.debug('~~~ Non matching Ids '+ l);

Related Solutions

[SalesForce] getting 3 random elements from a List

Try using remove. If you want to preserve the original list you could clone it into a placeholder so you're removing elements from a different collection. Doing so makes your method idempotent, so it is probably a good idea. Also it might be simpler to just use a while loop.

public List<Question> getActualQuestions()
{
    if (groupOneQuestions.size() <= 3) return groupOneQuestions;
    List<Question> actuals = new List<Question>();
    List<Question> clones = groupOneQuestions.clone();
    while (actuals.size() < 3)
    {
        Integer index = (Math.random() * (clones.size() - 1)).intValue();
        actuals.add(clones.remove(index));
    }
    return actuals;
}

Help to send data from one list to another using temporary object type

Instead of

...
        for(OppNegocioTemp i:listTempOppNegocios){
            oppNegocios.add(listTempOppNegocios(i));
        }
...

you need to have (notice that you need to call get on list to get an element or use array accessor [] notation instead of method call () notation)

...
        for(OppNegocioTemp i:listTempOppNegocios){
            oppNegocios.add(listTempOppNegocios.get(i));
        }
...

With that said, you could also achieve what you are trying to as follows without you looping.

oppNegocios.addAll(listTempOppNegocios)

Best Answer

Related Solutions

[SalesForce] getting 3 random elements from a List

Help to send data from one list to another using temporary object type

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