G.R.A.S.P | шаблоны проектирования

Summary

In this video, the speaker discusses the practical application of design patterns in object-oriented programming, based on insights from Krig Norman's book. They explain how initially confusing patterns, such as polymorphism, low coupling, and high cohesion, can be utilized to create flexible and scalable systems. The speaker also introduces five key roles—Creator, Controller, Information Expert, Pure Fabrication, and Mediator—which help distribute responsibilities in large software architectures. By focusing on these patterns, developers can achieve resilient systems that adapt to changes without disrupting other components, making these principles essential for effective architectural planning.

Takeaways

• 😀 Design patterns are tools for distributing responsibilities between classes and objects in object-oriented programming.
• 😀 Initially, the speaker struggled to understand Norman's design patterns, finding them incompatible with other concepts like SOLID.
• 😀 After revisiting the book and applying the patterns in large-scale systems, the speaker found value in adapting the principles to suit real-world scenarios.
• 😀 The property of 'resilience to changes' is central to the design patterns and refers to the ability of a system to handle modifications without impacting other parts.
• 😀 Resilience to changes is a global property of the system, not something that can be determined at the level of individual classes or objects.
• 😀 The speaker refined Norman's patterns into three principles: Polymorphism, Low Coupling/High Cohesion, and Responsibility Distribution.
• 😀 Polymorphism allows for code reuse and is closely related to the Strategy pattern, enabling flexibility in object behavior.
• 😀 Low coupling and high cohesion are key principles for creating maintainable and modular systems, reducing unnecessary dependencies between classes.
• 😀 The five roles proposed in Norman's patterns are: Creator, Controller, Information Expert, Pure Fiction, and Mediator. Each role has specific responsibilities within the system.
• 😀 The Creator role is responsible for creating objects, and it often aligns with the Abstract Factory pattern, providing flexibility in object initialization.
• 😀 The Mediator role helps reduce coupling between different classes by providing a central interface for communication, making the system more adaptable.
• 😀 The Pure Fiction role addresses tasks that don't belong to any specific expert but are necessary for the system, such as utility functions or system-wide tasks.
• 😀 These design patterns, when understood and applied correctly, can help ensure that a system is adaptable, easy to modify, and resilient to change.
• 😀 The speaker plans to provide further examples and video content, including practical demonstrations with Angular, depending on viewer interest and feedback.

Q & A

What are the main challenges the speaker faced when initially studying Norman's design patterns?

The speaker initially struggled with understanding Norman's design patterns, finding them abstract, impractical, and seemingly incompatible with other systems like the Jail framework. He believed that these patterns were not useful in real-world applications.

What did the speaker discover after revisiting Norman's patterns in the context of large-scale systems?

After revisiting the patterns in the context of building large-scale distributed systems, the speaker realized that the patterns are actually practical and useful, but they needed to be reinterpreted and classified more effectively.

How does the speaker describe the core challenge of achieving 'resistance to changes' in system design?

The core challenge lies in ensuring that when a part of the system changes, other parts are not negatively impacted. 'Resistance to changes' is a property of the entire system, not just individual classes, and it helps maintain system stability during updates.

What is the significance of 'resistance to changes' as a design property in software architecture?

'Resistance to changes' is crucial for creating systems that can evolve over time without causing extensive disruption. It ensures that parts of the system can be modified or replaced without breaking other components.

How are Norman's design patterns structured, according to the speaker's analysis?

Norman's design patterns are structured around three principles, one property, and five roles. These patterns focus on distributing responsibilities across the system in a way that reduces dependencies and increases flexibility.

What are the three principles mentioned in the speaker's interpretation of Norman's patterns?

The three principles are: polymorphism (enabling code reuse through interfaces), low coupling with high cohesion (reducing unnecessary interactions between classes), and maintaining high focus (ensuring classes are focused on solving specific problems).

Can you explain the five roles in the context of Norman's design patterns?

The five roles are: 1) Creator (responsible for creating objects), 2) Controller (manages input and processes requests), 3) Information Expert (holds knowledge and data about the domain), 4) Pure Fiction (handles business logic or system-specific tasks), and 5) Mediator (reduces dependencies between classes and manages communication).

Why does the speaker emphasize that the roles should rarely overlap?

The speaker emphasizes that roles should not overlap to avoid reducing system flexibility. Overlapping roles lead to increased coupling, making the system more difficult to maintain and adapt over time.

What role does the 'Information Expert' play in a system's architecture?

The 'Information Expert' role is responsible for managing and manipulating the data within the system. This role is typically associated with models that represent the domain and contain the logic for modifying the data they hold.

How does the 'Mediator' role contribute to system flexibility and adaptability?

The 'Mediator' role reduces direct coupling between classes by providing a central interface for communication. This allows different components to interact without being tightly linked, enabling easier modifications and ensuring that changes in one part of the system do not affect others.