Quick Start with Apex Development

Complete this quick start to create, test, and debug a workflow that is created using an Apex class, and sets off an Apex trigger.

We create a custom object called Book, and add a custom field called Price to that custom object. We update and test the updated Price field using Apex and learn how to work with Apex code using the Salesforce Extensions.

Create a Custom Object

Log in to your sandbox or Developer org.
Go to Setup > Object Manager > Create > Custom Object.
Enter Book for the label.
Enter Books for the plural label.
Click Save.
In the Custom Fields & Relationships section of the Book detail page, click New.
Select Number for the data type and click Next.
Enter Price for the field label.
Enter 16 in the length text box.
Enter 2 in the decimal places text box, and click Next.
Click Next to accept the default values for field-level security.
Click Save.

Add an Apex Class

In VS Code, connect to the org that you added the custom object to using the Org Picker or Command Palette.
Run the SFDX: Refresh SObject Definitions command from the Command Palette to get code completion suggestions for your SObjects related code.
Click the Cloud icon in the Activity Bar to open the Org Browser.
Scroll down to Custom Object and locate the Book_c object. Click the retrieve icon to run SFDX: Retrieve Source from Org.
From the Command Palette run SFDX:Create Apex Class and create a class called MyBooks.
Add a method called applyDiscount to this class.

Make this method both public and static. Because it’s a static method, you don’t need to create an instance of the class to access the method. Use the name of the class followed by a dot (.) and the name of the method.

1public with sharing class MyBooks {
2    public MyBooks() {
3
4    }
5    public static void applyDiscount(Book__c[] books) {
6        for (Book__c b : books){
7           b.Price__c *= 0.9;
8        }
9     }
10}

This method takes one parameter, a list of Book records, which is assigned to the variable books. The method iterates through a list of books and applies a 10% discount to the current book price.

Next, add a trigger that calls this applyDiscount method.

Add an Apex Trigger

An Apex trigger is a piece of code that executes before or after records of a particular type are inserted, updated, or deleted from the database. Every trigger runs with a set of context variables that provide access to the records that caused the trigger to fire.

From the Command Palette, run SFDX: Create Apex Trigger and create a class called MyBooksTrigger.
Update the default template to this trigger definition:

1trigger MyBooksTrigger on Book__c (before insert) {
2
3   Book__c[] books = Trigger.new;
4
5   MyBooks.applyDiscount(books);
6}

We now have the code that is needed to update the price of all books that get inserted.

Next, let’s add a test class and add a unit test. Unit tests are an important part of writing code and are required. In addition to ensuring the quality of your code, unit tests enable you to meet the code coverage requirements for deploying or packaging Apex. To deploy Apex or package it for AppExchange, unit tests must cover at least 75% of your Apex code, and those tests must pass.

Write a Unit Test

Now, add a test class with one test method. Then run the test and verify code coverage. The test method exercises and validates the code in the trigger and class. Also, it enables you to reach 100% code coverage for the trigger and class. For our example, create a test class that inserts a new book object that sets off the Apex trigger we wrote earlier.

To create the test class:

From the Command Palette, run SFDX:Create Apex Class and create a class called MyBooksTestClass.
Paste the following code in the MyBooksTestClass.cls file:

1@isTest
2private with sharing class MyBooksTestClass {
3    static testMethod void validateMyBooks() {
4       Book__c b = new Book__c(Name='Behind the Cloud', Price__c=100);
5       // Insert book
6       insert as user b;
7       // Retrieve the new book
8       Book b2 = [SELECT Price__c FROM Book__c WHERE Id =:b.Id WITH USER_MODE];
9      //Confirm that the price has been updated correctly
10       Assert.areEqual(90, b2.Price__c);
11      }
12}

This test class is defined using the @isTest annotation. We recommend that classes defined this way only contain test methods and any methods required to support those test methods. One advantage to creating a separate class for testing is that classes defined with @isTest don’t count against your org’s limit of 6 MB of Apex code. You can also add the @isTest annotation to individual methods. For more information, see isTest Annotation and Execution Governors and Limits.

Important

To run the test you wrote, you must deploy your code to your org. Right-click in the file and run SFDX: Deploy This Source to Org to deploy your code.
To test your code, click Run All Tests in the MyBooksTestClass file.