Behavioral Design Pattern

Behavioral patterns are concerned with algorithms and the assignment of responsibilities between objects. Behavioral patterns describe not just patterns of objects or classes but also the patterns of communication between them.

Importance of Behavioral Design Pattern

• These patterns characterize complex control flow that’s difficult to follow at run-time.
• They shift focus away from flow of control to let you concentratejust on the way objects are interconnected.
• Behavioral class patterns use inheritance to distribute behavior between classes.

When to ue Behavioral Design Patterns

• Communication Between Objects: Use behavioral patterns when you want to define how objects communicate, collaborate, and interact with each other in a flexible and reusable way.
• Encapsulation of Behavior: Apply behavioral patterns to encapsulate algorithms, strategies, or behaviors, allowing them to vary independently from the objects that use them. This promotes code reusability and maintainability.
• Dynamic Behavior Changes: Use behavioral patterns when you need to allow for dynamic changes in an object’s behavior at runtime without altering its code. This is particularly relevant for systems that require flexibility in behavior.
• State-Dependent Behavior: State pattern is suitable when an object’s behavior depends on its internal state, and the object needs to change its behavior dynamically as its state changes.
• Interactions Between Objects: Behavioral patterns are valuable when you want to model and manage interactions between objects in a way that is clear, modular, and easy to understand.

Advantages of Behavioral Design Patterns

Flexibility and Adaptability:

• Behavioral patterns enhance flexibility by allowing objects to interact in a more dynamic and adaptable way. This makes it easier to modify or extend the behavior of a system without altering existing code.
• Code Reusability:
• Behavioral patterns promote code reusability by encapsulating algorithms, strategies, or behaviors in separate objects. This allows the same behavior to be reused across different parts of the system.
• Separation of Concerns:
• These patterns contribute to the separation of concerns by dividing the responsibilities of different classes, making the codebase more modular and easier to understand.
• Encapsulation of Algorithms:
• Behavioral patterns encapsulate algorithms, strategies, or behaviors in standalone objects, making it possible to modify or extend the behavior without affecting the client code.
• Ease of Maintenance:
• With well-defined roles and responsibilities for objects, behavioral patterns contribute to easier maintenance. Changes to the behavior can be localized, reducing the impact on the rest of the code.

Disadvantages of Behavioral Design Patterns

• Increased Complexity: Introducing behavioral patterns can sometimes lead to increased complexity in the codebase, especially when multiple patterns are used or when there is an excessive use of design patterns in general.
• Over-Engineering: There is a risk of over-engineering when applying behavioral patterns where simpler solutions would suffice. Overuse of patterns may result in code that is more complex than necessary.
• Limited Applicability: Not all behavioral patterns are universally applicable. The suitability of a pattern depends on the specific requirements of the system, and using a pattern in the wrong context may lead to unnecessary complexity.
• Code Readability: In certain cases, applying behavioral patterns may make the code less readable and harder to understand, especially for developers who are not familiar with the specific pattern being employed.
• Scalability Concerns: As the complexity of a system increases, the scalability of certain behavioral patterns may become a concern. For example, the Observer pattern may become less efficient with a large number of observers.

Designing object-oriented software is hard, and designing reusable object-oriented software is even harder.

Christopher Alexander says, “Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice”.

Even though Alexander was talking about patterns in buildings and towns, what he says is true about object-oriented design patterns.