Run before update trigger on after insert

Question

So I have a trigger that I want to run everytime a record is updated and created. However, when I use after insert and before update I get a record is locked error when creating the record.

How can I run this trigger on both record edit and creation?

Better yet, is it possible to update any field "after update" or "after insert"?

trigger CalcBenefit on EA_App__c (before update, after insert) {
//works for update only.  insert throws error because I'm trying to change value
for (EA_App__C ea : Trigger.new){

    EA_App__C oldEA = Trigger.oldMap.get(ea.Id);

    if (ea.X3_Month_Income__c > CalculateBenefit.getMax(integer.valueOf(ea.Family_Size__c))){
        ea.App_Status__c = 'DENIED';            
        ea.Benefit_Amount__c = 0;                 

    }else if (ea.X3_Month_Income__c <= CalculateBenefit.getMin(integer.valueOf(ea.Family_Size__c)) && ea.App_Status__c != 'PAID'){
        //how to compare to old? 
        //&& (ea.X3_Month_Income__c != oldEA.X3_Month_Income__c || ea.Family_Size__c != oldEA.Family_Size__c)
        ea.Benefit_Amount__c = 0;                 
        ea.App_Status__c = 'SENT FOR APPROVAL';                

    }else{
        ea.App_Status__c = 'PAID';
        ea.Benefit_Amount__c = CalculateBenefit.calc(ea.X3_Month_Income__c, integer.valueOf(ea.Family_Size__c), ea.Fuel_Cost__c, '2015');
    }

}

}

Answer 1

You can use before insert to modify records before they're saved to the database, which should work well enough for your purposes.

You can simply set oldEA to a blank record, which will also satisfy your "changed fields" conditions:

EA_App__C oldEA = Trigger.isInsert? new EA_App__c(): Trigger.oldMap.get(ea.Id);

If it doesn't work, you can also choose to update the records recursively:

if(Trigger.isAfter && Trigger.isInsert) {
    update Trigger.new.deepClone(true);
} else {
    // Before Update Logic
}

Answer 2

Is there a reason that your trigger needs to be after insert rather than before insert? Usually, after insert is used to update other records in the database after this record has been inserted. You frequently need to wait so that you are sure that the record has its final data (all other before insert triggers have run). Salesforce stops you from changing values directly on the record because the record has already been committed to the database. Your value changes in the after trigger will not impact the record.

Some valid cases for needing an after trigger would be that you have cross-object formulas that you need to be calculated or you need the Id to get data from related records. If neither of these are the case I would suggest moving your trigger to operate before insert. If you must use after insert you will need to construct a new instance of your SObject and do another update DML statement.