trigger for auto number based on parent record salesforce

Question

I am working on one trigger to auto name child records based on Parent Record.

I have two objects which are having lookup relationship.

1) Build_Cycle__c

2) Action_Item__c

Auto number is working fine on creation but on deleting my trigger is not working.

lets say for one build cycle I have 4 action items

BUILD CYCLE:1

1) Actionitem1

2) Actionitem2

3) Actionitem3

4) Actionitem4

now count is 4 and if I delete Actionitem3 and creates Actionitem5 then count should be 5 but count is coming 4 only, can anyone help me out in this issue here if possible.

public class RenameActionItem {
public static void renameActionItemRecord(List<Action_Item__c> actionItemList){
    try{
        integer length1 = actionItemList.size();

        Set<Id> buildCycleId = new Set<Id>();
        for(Action_Item__c actionObj : actionItemList) {
            buildCycleId.add(actionObj.DCS_Build_Cycle__c);   
        }  

        List<Action_Item__c> actionItemList2 = new List<Action_Item__c>();
        actionItemList2 = [SELECT Id FROM Action_Item__c WHERE DCS_Build_Cycle__r.Id IN :buildCycleId]; 

        List<Build_Cycle__c> buildCycleList = new List<Build_Cycle__c>();
        buildCycleList = [SELECT Name, (SELECT Id FROM Action_Items__r) FROM Build_Cycle__c WHERE Id IN: buildCycleId];

        for(Build_Cycle__c bObj : buildCycleList){
            Integer length2 = bObj.Action_Items__r.size();

            for(Action_Item__c cObj : actionItemList){
                if(bObj.Id == cObj.DCS_Build_Cycle__c){

                    if(length2 < length2+length1){
                        cObj.Auto_Number__c = length2;

                    } 
                    length2++;

                }
            }
        }

    }catch(Exception e){
        System.debug('Exception in code'+e.getCause() + 'Exception in Line number'+e.getLineNumber());
    }
}
}

Trigger:

trigger Rename on Action_Item__c (before insert) {
if(trigger.isInsert && trigger.isBefore){
    RenameActionItem.renameActionItemRecord(trigger.new);
}
}

Answer 1

You are checking the size of the record list, SOQL query will take only the existing records not count against the deleted records. You can't check the size you should have to find out the last record's number(auto number ), you can try like this :

public class RenameActionItem {
public static void renameActionItemRecord(List<Action_Item__c> actionItemList){
    try{
        integer length1 = actionItemList.size();

        Set<Id> buildCycleId = new Set<Id>();
        for(Action_Item__c actionObj : actionItemList) {
            buildCycleId.add(actionObj.DCS_Build_Cycle__c);   
        }  

        List<Action_Item__c> actionItemList2 = new List<Action_Item__c>();
        actionItemList2 = [SELECT Id FROM Action_Item__c WHERE DCS_Build_Cycle__r.Id IN :buildCycleId]; 

        List<Build_Cycle__c> buildCycleList = new List<Build_Cycle__c>();
        buildCycleList = [SELECT Name, (SELECT Id,Auto_Number__c FROM Action_Items__r where order by id desc limit 1 ) FROM Build_Cycle__c WHERE Id IN: buildCycleId];

        for(Build_Cycle__c bObj : buildCycleList){
              string autoNumber = bObj.Action_Items__r[0].Auto_Number__c;
            Integer length2 = Integer.valueOf(autoNumber.replace('Actionitem',''))

            for(Action_Item__c cObj : actionItemList){
                if(bObj.Id == cObj.DCS_Build_Cycle__c){

                    if(length2 < length2+length1){
                        cObj.Auto_Number__c = length2;

                    } 
                    length2++;

                }
            }
        }

    }catch(Exception e){
        System.debug('Exception in code'+e.getCause() + 'Exception in Line number'+e.getLineNumber());
    }
}
}