Apex Trigger to create a Cross- Object Rollup Field

Question

I have created a custom Object called Application__c that has a lookup relationship to the Opportunity object. I have a field called total_applications__c on the Opportunity which aims to represent the total number of applications related to that opportunity.

I trying to populate that field though an apex trigger on the Application__c object that operates on after insert, after delete and after undelete events.

Considering the insert event :

My initial approach is that each time an application is being inserted I

-> create an oppset with all the opportunities that are being linked to from the applications that have been triggered

-> loop through all the applications that are link to an opportunity from the oppset

-> add the number of applications related to each opportunity in a map

-> loop though all the related opportunities from the applications that have currently being inserted

-> update that total_applications__c field with the computed values from the map.

However I feel that I can achieve the same functionality in fewer steps. Is there a better way of achieving what I described above?

Answer 1

You can use declarative-lookup-rollup-summaries for this purpose. You would then create a Lookup Rollup Summary something like:

• Parent Object: Opportunity
• Relationship Field: Opportunity__c
• Child Object: Application__c
• Field to Aggregate: Id
• Aggregate Operation: Count
• Aggregate Result Field: Total_Applications__c

Clicks not code!