Why do we need Composite Design Pattern?

The Composite Design Pattern was created to address specific challenges related to the representation and manipulation of hierarchical structures in a uniform way. Here are some points that highlight the need for the Composite Design Pattern:

1. Uniform Interface:
   • The Composite Pattern provides a uniform interface for both individual objects and compositions.
   • This uniformity simplifies client code, making it more intuitive and reducing the need for conditional statements to differentiate between different types of objects.
   • Other design patterns may not offer the same level of consistency in handling individual and composite objects.
2. Hierarchical Structures:
   • The primary focus of the Composite Pattern is to deal with hierarchical structures where objects can be composed of other objects.
   • While other patterns address different types of problems, the Composite Pattern specifically targets scenarios involving tree-like structures.
3. Flexibility and Scalability:
   • The Composite Pattern allows for dynamic composition of objects, enabling the creation of complex structures.
   • It promotes flexibility and scalability, making it easier to add or remove elements from the hierarchy without modifying the client code.
4. Common Operations:
   • By defining common operations at the component level, the Composite Pattern reduces code duplication and promotes a consistent approach to handling both leaf and composite objects.
   • Other design patterns may not provide the same level of support for common operations within hierarchical structures.
5. Client Simplification:
   • The Composite Pattern simplifies client code by providing a unified way to interact with individual and composite objects. This simplification is particularly valuable when working with complex structures, such as graphical user interfaces or organizational hierarchies.

The Composite Design Pattern is a structural design pattern that lets you compose objects into tree-like structures to represent part-whole hierarchies. It allows clients to treat individual objects and compositions of objects uniformly. In other words, whether dealing with a single object or a group of objects (composite), clients can use them interchangeably.

As described by the Gang of four, “Compose objects into tree structure to represent part-whole hierarchies. Composite lets client treat individual objects and compositions of objects uniformly”.

The key concept is that you can manipulate a single instance of the object just as you would manipulate a group of them. The operations you can perform on all the composite objects often have the least common denominator relationship.