Quick Start Apex Development with Salesforce Extensions

Quick Start Apex Development

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

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

Before you start, install Salesforce Extensions for Desktop or Set Up Code Builder

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

Connect to the org that you added the custom object to in VS Code.
Run the SFDX: Refresh SObject Definitions command from the Command Palette to get completion suggestions for your SObjects related code.
Scroll down to Custom Object in the Org Browser 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 MyHelloWorld.
Add a method called applyDiscount to this class.

We’ll 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—you can just use the name of the class followed by a dot (.) and the name of the method.

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:

public with sharing class MyHelloWorld {
    public MyHelloWorld() {

    }
    public static void applyDiscount(Book__c[] books) {
        for (Book__c b :books){
           b.Price__c *= 0.9;
        }
     }
}

Next we’ll 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 Lightning Platform 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 new class called HelloWorldTrigger.
Update the default template to this trigger definition:

trigger HelloWorldTrigger on Book__c (before insert) {

   Book__c[] books = Trigger.new;

   MyHelloWorld.applyDiscount(books);
}

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.

Write a Unit Test

Now we’ll add a test class with one test method. We’ll also 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, we’ll create a test class that inserts a new book object which 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 HelloWorldTestClass.
Paste the following code in the HelloworldTestClass.cls file:

@isTest 
private class HelloWorldTestClass {
    static testMethod void validateHelloWorld() {
       Book__c b = new Book__c(Name='Behind the Cloud', Price__c=100);
       // Insert book
       insert b;    
       // Retrieve the new book
       b = [SELECT Price__c FROM Book__c WHERE Id =:b.Id];
//Confirm that the price has been updated correctly
       System.assertEquals(90, b.Price__c);
      }
}

Note :::note This test class is defined using the @isTest annotation. Classes defined this way should 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. :::

To run the test you wrote, you must deploy your code to your org. Right-click within the file and run Run SFDX: Deploy This Source to Org to deploy your code.
Run SFDX: Turn On Apex Debug Log for Replay Debugger to turn on debug logs.
Click “Run All Tests” in the HelloWorldTestClass file to run your test.

Debug Your Code Using Apex Replay Debugger

With your code deployed in the org, you’re ready to use the Apex Replay Debugger to debug your code. The Replay Debugger uses debug logs generated in your org to replay a test scenario.

Run SFDX: Get Apex Debug Logs and select the topmost file from the list to get the most recent debug log. The log file opens.
Open the HelloWorldTestClass.cls file and set a breakpoint on Decimal b_price = b.Price__c;.
Set another breakpoint on Book__c[] books = Trigger.new; in the HelloWorldTrigger.trigger file.
Open HelloWorldTestClass.cls file and run SFDX: Launch Apex Replay Debugger with Current File from the Command Palette to generate and load the debug log file and launch the replay debugger.
Step through the code and check variable values.
Your debugging session automatically ends when the test is complete.

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