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Behavioral Design Patterns

In the realm of software engineering, design patterns are tried-and-true solutions to common problems that developers face. Among the various categories of design patterns, behavioral patterns stand out as they focus on algorithms and the assignment of responsibilities between objects. They help in managing complex control flows and simplify the communication between objects.

In this comprehensive guide, we'll delve into the world of behavioral design patterns, explore their importance, and provide detailed explanations and examples of some of the most widely used patterns.

What Are Behavioral Design Patterns?​

Behavioral design patterns are design patterns that identify common communication patterns between objects. By doing so, these patterns increase flexibility in carrying out communication. They help in:

  • Defining how objects interact.
  • Increasing the flexibility of code by allowing new behaviors to be added with minimal changes.
  • Managing complex control flows in a clean and understandable way.

Below are the key types of Behavioral Design Patterns:

Behavioral Design Pattern

1. Observer​

  • The Subject maintains a list of Observer objects.
  • When the Subject's state changes, it notifies all Observer objects.

2. State​

  • The Context holds a State object.
  • The State object defines the behavior of the Context, and the Context delegates to it.

3. Chain of Responsibility​

  • Requests are passed along a chain of Handler objects.
  • Each Handler decides whether to handle the request or pass it to the next Handler in the chain.

4. Command​

  • The Command object encapsulates a request as an object.
  • The Command object calls the Receiver object to perform the action.

5. Iterator​

  • The Iterator object provides a way to access elements of a collection sequentially.

6. Mediator​

  • The Mediator object centralizes communication between Colleague objects.
  • Colleague objects communicate with each other through the Mediator.

7. Memento​

  • The Originator creates Memento objects to save its internal state.
  • The Caretaker stores Memento objects.

8. Interpreter​

  • The Interpreter uses an Expression to interpret the context.
  • It defines a grammatical representation for a language and provides an interpreter to deal with this grammar.

Why Use Behavioral Patterns?​

Improved Flexibility​

They allow algorithms to vary independently from the clients that use them.

Reusability​

Common behaviors can be reused across different parts of an application.

Maintainability​

By clearly defining object interactions, code becomes easier to maintain and extend.

Loose Coupling​

Reducing dependencies between objects leads to systems that are easier to evolve over time.

Behavioral Design Patterns

Explanation of the Diagram​

This diagram provides a high-level overview of common behavioral design patterns. Each set of interactions represents a different pattern: