Behavioural Design Pattern: Iterator Design pattern

Define Iterator Design Pattern

This pattern allows you to access elements from a collection in a sequential order without disclosing the underlying structure. It has read-only access and no access to the internal collection.

Examples of Iterator Patterns

Examples of iterator patterns include:

• Collection Iteration
• Collection Elements Ordering (Asc, Desc)

Iterator pattern with UML Diagram

The classes, interfaces, & objects in the above UML class diagram are defined as follows.

• Client: This class includes an object collection and uses the iterator's Next action to retrieve objects from the aggregate in the appropriate order.
• Iterator: This interface defines operations for accessing collection elements in a sequential order.
• ConcreteIterator: This class implements the Iterator interface.
• Aggregate: This interface describes the operation for creating an iterator.
• ConcreteAggregate: This class implements the Aggregate interface.

When Should You Use the Iterator Design Pattern?

The iterator design pattern is useful for the following cases:

• Allows sequential access to the elements of a collection object without understanding the underlying structure.
• Multiple or concurrent iterations are necessary for collection elements.
• Offers a standardized interface for accessing the collection elements.

Advantages of the Iterator Design Pattern

• Separation of Concerns: separates the iteration algorithms from the collection classes themselves.
• Multiple Traversals: Enables various ways to traverse a collection at the same time.
• Uniform Interface: Provides a consistent interface for accessing various data structures.
• Encapsulation: Captures the internal structure of a collection's navigation and access.