Platform Developer I Certification Maintenance (Winter ’25)

Iterable Variable in For Loops

What Is the Iterable Interface?
In Apex, Iterable enables you to:
Create custom classes that return a collection.
Iterate on that class with a for loop, just like you would on a list or set.
This is useful when:
You require custom iteration logic (e.g., filtering, batching).
You prefer clean and consistent looping syntax.

Steps to Implement and Use Iterable in Apex

1. Create a Class That Implements Iterable<T>

public class MyIterable implements Iterable {
private List strings;

// Constructor that initializes the strings field with the provided list
public MyIterable(List<String> strings) {
    this.strings = strings;
}

// Iterator method that returns an iterator for the strings list
public Iterator<String> iterator() {
    return strings.iterator();
}
}

2. Create a Test Class

@IsTest
public class MyIterableTest {

@IsTest
static void testIterableForLoop() {
    // Step 1: Create a list of strings
    List<String> strings = new List<String>{'Hello', 'World'};

    // Step 2: Create an instance of MyIterable with the list of strings
    MyIterable myIterableInstance = new MyIterable(strings);

    // Step 3: Add a debug statement to verify test execution
    System.debug('Running the for loop...');

    // Step 4: Use a for loop to iterate over the MyIterable instance
    for (String str : myIterableInstance) {
        // Step 5: Print each string using System.debug
        System.debug('String: ' + str);
    }
}

}