OrgReady

Salesforce Skills & Readiness

← Prepare for Senior / Lead Roles

Lesson 15 of 18 · 10–15 min

Variables and Collections

A strong Apex foundation prevents small syntax lessons from turning into unsafe production patterns.

Learning sequence · data model first, security layers next
  1. What CRM and Salesforce Do
  2. The Salesforce Ecosystem and Major Clouds
  3. Org, App, Object, Field, and Record
  4. Standard and Custom Objects
  5. Common Standard Objects
  6. Field Types and Data Quality
  7. Objects, Fields & Records
  8. Lookup vs Master-Detail
  9. Many-to-Many Relationships and Junction Objects
  10. Profiles, Permission Sets & Object Access
  11. Field-Level Security
  12. OWD and Least-Privilege Record Access
  13. Opening Access: Role Hierarchy, Sharing Rules, Public Groups & Apex Sharing
  14. Apex First Steps
  15. Variables and Collections
  16. SOQL and DML Basics
  17. Why Asynchronous Apex Exists
  18. REST Callout Introduction

Your focus

Prepare for Senior / Lead Roles

CHECKPOINT · Checkpoint • Design

  • Check platform limits, transaction boundaries, and production trade-offs.

Learning objective

Explain and apply variables and collections in a small Salesforce scenario.

The concept

Variables hold typed values. List preserves an ordered collection, Set keeps unique values, and Map provides values by key. Collection-first thinking is essential for triggers, queries, and bulk DML.

Worked example

Collect Account IDs in a Set, query matching records once, then index them in a Map.

Read the requirement, identify the records and transaction, run the smallest example in a safe environment, inspect the result, and then add tests and bulk considerations before production use.

List, Set, and Map

apex

List<String> names = new List<String>{'Acme', 'Globex'};
Set<Id> accountIds = new Set<Id>();
for (Contact contact : Trigger.new) {
    if (contact.AccountId != null) accountIds.add(contact.AccountId);
}
Map<Id, Account> accountsById = new Map<Id, Account>(
    [SELECT Id, Name FROM Account WHERE Id IN :accountIds]
);

Common mistake

Copying a single-record example into automation without considering collections, limits, errors, or testability.

Interview angle

Explain the platform reason behind the syntax and state how the approach behaves for many records.

Pause and apply

What changes when this operation handles 200 records instead of one?

Official references

Reviewed 2026-09-23. Examples are illustrative; no code is executed here.

Key takeaways

  • Apex runs inside governed transactions.
  • Collections and bulk operations are the normal production shape.

Practice next

No linked assessment is available for this lesson. Use the pause-and-apply question to check your reasoning.

Reading these lessons does not yet save completion. Challenge results continue to provide assessment evidence.