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Trigger.oldMap in Salesforce| Context Variables in Apex Triggers
Chapter Topics
- Basics of Triggers
- When to use triggers
- Types of Apex Triggers in Salesforce
- Trigger Order of Execution
- Trigger Context Variables in Salesforce
- Trigger.new in Salesforce| Context Variables in Apex Triggers
- Trigger.old in Salesforce | Context Variables in Apex Triggers
- Trigger.newMap in Salesforce| Context Variables in Apex Triggers
- Trigger.oldMap in Salesforce| Context Variables in Apex Triggers
- Trigger Exceptions
- Best Practice in Triggers
- Trigger Helper Class Pattern
Trigger.oldMap in Salesforce returns a map of record IDs to the old version of sObject records, and is available in update and delete triggers.
Trigger.oldMap Example:
| trigger OpportunityTrigger on Opportunity (before update) { Map<Id, Opportunity> oMap = Trigger.oldMap; for (Opportunity newOpp : Trigger.new) { Opportunity oldOpp = oMap.get(newOpp.Id); if (newOpp.Amount != oldOpp.Amount) { newOpp.Amount.addError(‘Amount cannot be changed’); } } } |
In this example, Trigger.oldMap helps compare old and new Opportunity records, ensuring that certain fields, like Amount, are not altered during the update.
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