Your First Trigger
By the end of this lesson, you'll be able to:
- Write a complete, working trigger from scratch
- Combine trigger context variables with real business logic
- Trace through what the trigger does for a specific insert scenario
Prerequisites: "Trigger Context Variables"
The scenario
A sales team wants every new Opportunity with an Amount over R100,000 automatically flagged as high-priority by setting a custom Priority__c field to 'High' — without a sales rep needing to remember to set it manually every time.
The complete trigger
trigger OpportunityTrigger on Opportunity (before insert) {
for (Opportunity opp : Trigger.new) {
if (opp.Amount != null && opp.Amount > 100000) {
opp.Priority__c = 'High';
}
}
}Every piece here has already been covered: before insert (Lesson 2 — modifying a field, so it must run before the save), Trigger.new (Lesson 3 — the records being inserted), and a plain if statement (Module 6) applying the actual business rule.
Tracing through a specific insert
Opportunity opp = new Opportunity(Name = 'Big Deal', Amount = 150000, StageName = 'Prospecting', CloseDate = Date.today());
insert opp;
System.debug(opp.Priority__c); // 'High'insert opp triggers OpportunityTrigger automatically; inside it, Trigger.new contains opp; opp.Amount (150000) is greater than 100000, so Priority__c gets set to 'High' before the actual save — the inserted record ends up with Priority__c already correctly populated, with zero extra code required at the call site.
Exercise
Write a before insert trigger on Case that sets a custom field Is_Urgent__c to true whenever the Case's Priority field equals 'High'.
Show hint
if (c.Priority == 'High') { c.Is_Urgent__c = true; }
Your First Trigger Quiz
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Summary
This lesson writes one complete, working trigger end to end, combining everything from this module's first three lessons into a real, useful piece of automation.