Module 6: Creating Triggers

In this module, you create a trigger that sends confirmation emails to speakers when they are assigned to a session. You create another trigger that rejects double bookings of speakers.

Step 1: Create a Trigger that Sends Confirmation Emails

In this step, you create a trigger that sends confirmation emails to speakers when they are assigned to a session.

1. In the Developer Console, click File > New > Apex Trigger

2. Specify SendConfirmationEmail as the trigger name, Session_Speaker__c as the sObject, and click Submit

3. Implement the trigger as follows:

   trigger SendConfirmationEmail on Session_Speaker__c (after insert) {
   
       for(Session_Speaker__c newItem : trigger.new) {
   
           // Retrieve session name and time + speaker name and email address
           Session_Speaker__c sessionSpeaker =
               [SELECT Session__r.Name,
                       Session__r.Session_Date__c,
                       Speaker__r.First_Name__c,
                       Speaker__r.Last_Name__c,
                    Speaker__r.Email__c
                FROM Session_Speaker__c WHERE Id=:newItem.Id];
   
           // Send confirmation email if we know the speaker's email address
           if (sessionSpeaker.Speaker__r.Email__c != null) {
               String address = sessionSpeaker.Speaker__r.Email__c;
               String subject = 'Speaker Confirmation';
               String message = 'Dear ' + sessionSpeaker.Speaker__r.First_Name__c +
                   ',\nYour session "' + sessionSpeaker.Session__r.Name + '" on ' +
                   sessionSpeaker.Session__r.Session_Date__c + ' is confirmed.\n\n' +
                   'Thanks for speaking at the conference!';
               EmailManager.sendMail(address, subject, message);
           }
       }
   
   }
   

   Make sure the trigger is defined to execute after insert on the first line of the trigger definition: you only want to send a confirmation email when the record has been successfully inserted and the record Id has been assigned.

   In a real-life application, hardcoding the email message is not a recommended approach. Consider using email templates instead.

4. Save the file. The trigger takes effect as soon as you save it.

5. Test the trigger

   • Create a speaker that has your own email address
   • Assign that speaker to a session, and check your email: you should receive a speaker confirmation email

Sending a confirmation email when a speaker is assigned to a session (in other words, when a Session_Speaker__c record is created) can be accomplished without writing code by defining a workflow rule. The programmatic approach used in this workshop allows you to satisfy additional requirements. For example, sending a confirmation email "on demand", independently of a record being created or updated.

Step 2: Create a Trigger that Rejects Double Bookings

1. In the Developer Console, click File > New > Apex Trigger

2. Specify RejectDoubleBooking as the trigger name, Session_Speaker__c as the sObject, and click Submit

3. Implement the trigger as follows:

   trigger RejectDoubleBooking on Session_Speaker__c (before insert, before update) {
   
       for(Session_Speaker__c sessionSpeaker : trigger.new) {
   
           // Retrieve session information including session date and time
           Session__c session = [SELECT Id, Session_Date__c FROM Session__c
                                   WHERE Id=:sessionSpeaker.Session__c];
   
           // Retrieve conflicts: other assignments for that speaker at the same time
           List<Session_Speaker__c> conflicts =
               [SELECT Id FROM Session_Speaker__c
                   WHERE Speaker__c = :sessionSpeaker.Speaker__c
                   AND Session__r.Session_Date__c = :session.Session_Date__c];
   
           // If conflicts exist, add an error (reject the database operation)
           if(!conflicts.isEmpty()){
               sessionSpeaker.addError('The speaker is already booked at that time');
           }
   
       }
   
   }
   

4. Save the file

5. Test the trigger:

   • Assign a speaker to a session scheduled at a time the speaker is available and make sure it still works
   • Assign a speaker to a session scheduled at the same time as another session the speaker is already assigned to: you should see the error message

RejectDoubleBooking is not sufficient to entirely prevent the double booking of speakers. For example, the user could change the date and time of a session after the facts in a way that creates a double booking for a speaker assigned to that session. You could create an additional trigger to take care of that situation.