How to write the trigger using after in one object should insert in 2 objects and update in one object at the same time

Question

I have a Custom Object A with start date and end date. It should insert weekly records in Custom Object B and Daily records in Custom Object C and should populate the Custom OBject B in it.

1. I have used after insert on Custom Object A which will insert Custom Object B and C.
2. written trigger on Custom Object B which will update the ID on Custom Object C.

Here both triggers are getting fired on the same object C.

Trigger TriggerInsertTime on Custom_Object A (after insert) {
List<CustomObjectA> CustomObjectAlist = new List<CustomObjectA>()
List<CustomObjectB> CustomObjectBlist = new List<CustomObjectB>()
List<CustomObjectC> CustomObjectClist = new List<CustomObjectC>()
for(Custom Object A a : trigger.New){
CustomObjectAlist .add(a);
}
for(CustomObjectA a1:CustomObjectAlist){
CustomObjectB = new CustomObjectB();
for(Integer i=0;i<3;i++){
b.a1 = a1.id;
b.stdt = a1.startdate;
b.enddt = a1. enddate;}
CustomObjectBlist.add(b);
CustomObjectC c = new CustomObjectC();
Integer numberDaysDue = a1.startdate.daysBetween(EndDate);
for(Integer j=0;j<numberDaysDue;j++){
            c.Date__c = stdt.addDays(j);
            c.a1 = a1.id;
                CustomObjectClist .add(c);
      }

insert CustomObjectBlist;
insert CustomObjectClist;
}

After insert both objects I want to update CustomObjectB Id in CustomObject C.

trigger Updatefield on CustomObjectB(after insert)
List<CustomObject C> updatetimeperiod = new List<CustomObject C>();
       for(CustomObjectB t2: tlist){
           
           id vid = t2.a1;
           for(CustomObject C tp1: [select id,date__c from CustomObject C where 
                                   t2 =:vid]){
                                       
                                       if(tp1.date__c>=t2.start_Date__c && tp1.date__c<=t2.End_Date__c){
                                           system.debug('date'+tp1.date__c);
                                           tp1.Time__c = t2.id;
                                           system.debug('tp1'+tp1.Time__c);
                                           updatetimeperiod.add(tp1);
                                       }
                                   }}
            if(updatetimeperiod.size()>0){
                system.debug('updatetimeperiod.size()'+updatetimeperiod.size());
                Update updatetimeperiod;}

when I insert and update on CustomObjectC at the same time am getting the following error:

getmessageBefore Insert or Upsert list must not have two identically equal elements

How to avoid trigger to fire at the same time. Is there anyway i can update after insert like can I use database.insert.Can anyone please help me on this issue?

Answer 1

You're literally adding the same object instance to your insert list over and over. Here's the relevant lines for Custom Object C, although you do this for both B and C:

CustomObjectC c = new CustomObjectC();
for (Integer j=0; j < numberDaysDue; j++) {
    CustomObjectClist.add(c);
}

insert CustomObjectClist;

CustomObjectClist consists of the same object instance repeated j times, because you create the instance outside the loop and never reinitialize it. The instance creation should be inside the loop if you wish to create multiple records.

You'll need to correct this for both B and C. There are multiple problems here, including an un-bulkified query in your B trigger, but that's the proximate issue.

Edit

Your query,

select id,date__c from CustomObject C where t2 =:vid

matches nothing because you're querying for child objects of Custom Object B while in a Custom Object B after insert trigger. It is not possible for an object to have children in its own after insert context as the object itself has not yet been committed.

I don't have a good understanding of what you're doing here but I suspect your Object B trigger really should be on Object C.