Salesforce Tutorial# 10: Introduction to Apex Triggers

Apex is an object-oriented, strongly typed programming language, API supported by to give transaction control on salesforce platform. Apex supports for online SOQL and SOSL query handling and returns SObjects records. It has built-in support for DML and DML exception handling. It is easy to understand and use as the syntax is more similar to Java language.

Apex is used to implement complex business functionality. Apex supports ‘Trigger‘. We can perform complex validation using Apex.

Note: SObject class is a generic class that can be any SFDC object.

Introduction of Collection Types, Loops & DML Statements

As per other programming languages, Apex also has some inbuilt data structures. Collectively it is called Collection. Apex Collection has four types namely Lists, Sets, Maps, and Enumerations. The first element of any collection type is always indexed at location zero.


A list is a sequential collection of elements. It allows duplicates. Let’s consider the following example to  create List of integer

You can also use the array syntax for lists. For example:

Set :

A set is another collection type. Unlike List, the set is unordered as well as doesn’t allow duplicates.


Maps are collections of types that support key-value pairs.


Consider the following example to create enumerated data types in Apex

Loops :

Apex supports five types of procedural loops. Following are the listed loops. All loops allow break and continue statements.

  • do{statement} while (condition);
  • while(conditionstatement;
  • for(initializationexit conditionincrementstatement;
  • for(variable : array/setstatement;
  • for(variable : [inline_soql_query]) statement;

Do-While Loops
Similar to other programming languages ​ do-while loop repeatedly executes a block of code till the Boolean condition remains true. Its syntax is:

While Loops

The Apex​​ while loop executes a block of code until a particular Boolean condition remains true. Its syntax is:

For Loop:

Apex supports three variations of the for loop:

  • The traditional for loop:

  • The list or set iteration for loop:

  • The SOQL for loop:

Here both variable and variable_list must be of the same sObject type.

Implementation of Apex Trigger

Apex triggers work like stored procedures execute when a particular event occurs. One can write pre-event and post-event trigger. e.g.

Triggers are executed using events like insert, update, delete, upsert, merge, undelete etc.

Example 1

Suppose we received a business requirement that we need to create a Payroll Record when Employee’s ‘Present Status’ field changes to present from absent. For this, we will create a trigger on APEX_Employee_c object by the following steps:

Step 1: Go to sObject

Step 2: Click on Employee

Step 3: Click on ‘New’ button in Trigger related list and add the trigger code as given below.

Understanding & Use of Trigger Context Variables

All triggers use context variables which allow to access data at run time. These variables can be accessed thru Trigger class. Eg. Trigger, old, Trigger.isExecuting, Trigger.oldMap etc.



isExecuting It returns true if the current context of the Apex code is a trigger
isInsert It will return true if it is fired by insert operation
isUpdate It will return true if it is fired by update operation
isDelete It will return true if it is fired by delete operation
isBefore It will return true if it is fired by before operation
isAfter It will return true if it is fired by afterall operation
isUndelete It will return true if  date is recovered from recycle bin
new It returns a list of the new versions of the sObject records.
newMap It returns a map of IDs for  sObject records.
old Returns a list of the old versions of the sObject records.
oldMap A map of IDs to the old map of the sObject records.
size The total number of records in a trigger invocation, both old and new.

 That’s all for a brief introduction to Apex. If you need to refer old tutorials please feel free to read them using below links

Tutorial Index

  1. Introduction to Cloud Computing ( and
  2. Overview of Database Concepts (
  3. Introduction to
  4. Building Salesforce Custom App and Objects
  5. Object Relationships and Formula Field in Salesforce
  6. Salesforce Security Model and Overview
  7. Automation in Salesforce
  8. Approval Process in Salesforce
  9. Introduction to SOQL and SOSL
  10. Introduction to Apex
  11. Salesforce Data Management
  12. Visualforce MVC Architecture on Cloud
  13. Salesforce Reports and Dashboards
  14. Building a Visualforce (Custom) Page for the Salesforce App
  15. Salesforce Sandbox and Overview of capabilities
  16. Learning Apex and Deployment Tools


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