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John King20 Why use Trigger.oldMap
Hi,
Appreciate any help here. New to Apex
I have code which updates on Contacts when Account is updated. I put the code together with the assistance of some code snippets I found online and put the rest of it together based off the requirements.
I'm trying to understand the reason for the use of Trigger.New and Trigger.oldMap. They are concepts I'm not fully familiar with and want to make sure I understand them.
Thanks for any help
Appreciate any help here. New to Apex
I have code which updates on Contacts when Account is updated. I put the code together with the assistance of some code snippets I found online and put the rest of it together based off the requirements.
I'm trying to understand the reason for the use of Trigger.New and Trigger.oldMap. They are concepts I'm not fully familiar with and want to make sure I understand them.
Thanks for any help
for(Account account : [SELECT Id, Total__c, (SELECT Id FROM Contacts) FROM Account WHERE Id IN :Trigger.new]){
if(account.Total__c != Trigger.oldMap.get(account.id).Total__c){
Integer numContacts = account.Contacts.size();
Decimal shareOfTotal = account.Total__c.divide(numberOfContacts,2)
Let say its Name earlier its was Abc and you are updating it with Xyz.
You will have two list now Trigger.new and Trigger.old
Trigger.old will hold Name of Account as Abc and Trigger.new will hold it as Xyz before they are commited to database.
Trigger.oldMap is just a Map with Id as Key mapped with with value same as you have with Trigger.Old.
Similarly you have Trigger.newMap as well i.e a Map with ID as key as value will be the newest one.
In your code
account.Total__c != Trigger.oldMap.get(account.id).Total__c
account.Total__c. ---> will hold the new value of filed Total.
Trigger.oldMap.get(account.id).Total__c------->
Trigger.oldMap.get(account.id) till this part it will return you Account with field having value before update is done
Trigger.oldMap.get(account.id).Total__c---> this will give the value of Specific total
it will hold the earlier value of Total.
The pupose of putting this check is to make sure that block of code only execute if there is change in Total__c Value . If update is done to other field and Total__c value is same then this block of code won't execute.
I hope I made it clear.
If it helps mark it as best answer.
Thanks!
All Answers
Let say its Name earlier its was Abc and you are updating it with Xyz.
You will have two list now Trigger.new and Trigger.old
Trigger.old will hold Name of Account as Abc and Trigger.new will hold it as Xyz before they are commited to database.
Trigger.oldMap is just a Map with Id as Key mapped with with value same as you have with Trigger.Old.
Similarly you have Trigger.newMap as well i.e a Map with ID as key as value will be the newest one.
In your code
account.Total__c != Trigger.oldMap.get(account.id).Total__c
account.Total__c. ---> will hold the new value of filed Total.
Trigger.oldMap.get(account.id).Total__c------->
Trigger.oldMap.get(account.id) till this part it will return you Account with field having value before update is done
Trigger.oldMap.get(account.id).Total__c---> this will give the value of Specific total
it will hold the earlier value of Total.
The pupose of putting this check is to make sure that block of code only execute if there is change in Total__c Value . If update is done to other field and Total__c value is same then this block of code won't execute.
I hope I made it clear.
If it helps mark it as best answer.
Thanks!
Trigger.old returns List of sObject records eg: List<Contact>
&&
Trigger.oldMap returns a map of old version of ids eg: <Id, Contact>
It can only be used in update, delete triggers.
You may want to go through the below documentation link to understand the trigger context variables.
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_triggers_context_variables.htm
Thanks,
Rohit