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@jmahmood
Last active November 7, 2017 05:07
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Don't do this in Salesforce please.
// Salesforce attracts programmers that have spent too much time using the same languages
// their whole life, without appropriate 'adventures' into other languages. It shows sometimes.
// IMO APEX doesn't really go out of its way to advertise its various collection types like Python
// or scripting languages & functional languages do. As a result, you end up reinventing the wheel a lot.
// Wrong way, don't do this.
List<Id> LstParentId = new List<Id>();
if (newList != null)
{
for (SObject newObj : newList) {
boolean fAlreadyExist = false;
For(id idCurrent : LstParentId)
{
if (idCurrent == (Id)newObj.get('ParentId__c'))
{
fAlreadyExist = true;
}
}
if (!fAlreadyExist)
{
LstParentId.Add((Id)newObj.get('ParentId__c'));
}
}
}
if (oldList != null)
{
for (SObject newObj : oldList) {
boolean fAlreadyExist = false;
For(id idCurrent : LstParentId)
{
if (idCurrent == (Id)newObj.get('ParentId__c'))
{
fAlreadyExist = true;
}
}
if (!fAlreadyExist)
{
LstParentId.Add((Id)newObj.get('ParentId__c'));
}
}
}
// What is wrong? For one, you are repeating code on many different levels. Let's fix that.
// PS, this is still wrong.
for (List<SObject> l : new List<List<SObject>> {newList, oldList}){
if (l != null){
for (SObject newObj : newList) {
boolean fAlreadyExist = false;
For(Id idCurrent : LstParentId)
{
if (idCurrent == (Id)newObj.get('ParentId__c'))
{
fAlreadyExist = true;
}
}
if (!fAlreadyExist)
{
LstParentId.Add((Id)newObj.get('ParentId__c'));
}
}
}
}
// You may complain that there is an "additional heap allocation";
// please wake up, we are on SFDC, not doing assembly on a micro controller.
// You are far more limited by code size (3mb total) than in-memory allocations.
// ------
// The other problem is poor collection choices. What are you actually doing in this loop?
// You are trying to get unique IDs from a list of objects.
// Lists are good for when order matters, but order does not matter in this example.
// What matters is the unique IDs.
// APEX has the Set object, which typically keeps an *unorganized, unique collection of objects.
// Using Sets, Your code becomes this:
Set<Id> set_parent_id = new Set<Id>();
for (List<SObject> l : new List<List<SObject>> {newList, oldList}){
if (l != null){
for (SObject obj : l) {
set_parent_id.add((Id)obj.get('ParentId__c'));
}
}
}
// 8 Lines vs. 36 lines; much easier to keep tabs on.
// * SFDC set order is predictable (which is weird for those of us from other languages). It doesn't matter though.
// http://releasenotes.docs.salesforce.com/en-us/summer15/release-notes/rn_apex_maps_and_sets_iteration_order.htm
@jmahmood
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jmahmood commented Nov 7, 2017

In US.SFDC, it would be:

Set<Id> set_parent_id = new Set<Id>();
set_parent_id.addAll((List<Id>) US.OL(newList).pluck(List<Id>.class, 'ParentId__c'));
set_parent_id.addAll((List<Id>) US.OL(oldList).pluck(List<Id>.class, 'ParentId__c'));

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