Design Pattern's,
Code Smells
Design Pattern's
Few Books
- Apply UML and Patterns - GRASP Craig Larman
- Design Patterns - GoF - Eric Gama, Richard Helm, Ralph Jhonson, Jhon Vlissedes
- Patterns of Enterprise Application Architecture - Martin Fowler
- Enterprise Integration Patterns - Gregor Hohpe & Bobby Wolf
- Refactoring to Patterns - Joshua Kerlevsky
- Refactoring to Patterns - Martin Fowler
- Analysis Patterns - Martin Fowler
- xUnit Test Patterns - Gerard Meszaros
2
What is Design Pattern
Design patterns are optimized, reusable solutions to the programming problems that we encounter every day.
Design Patterns are Recipies
You have a problem statement - and you have a solution
What if your problem is not a perfect match?
Do not force design pattern
How to solve the problem?
Understand how design patterns are defined in first place, and help yourself to come up with a variant of a solution.
How is Design Pattern or any Pattern defined?
Here comes some philosophical rant?
Pattern - is a solution to a problem, based on principle(s) and a valid context.
What is Principle?
A fundamental truth or proposition that serves as the foundation for a system of belief or behavior or chain of a reasoning
Which Principles?
Software Design Principle or Object Oriented Principles or any other principles
Why to study Design Patterns and Not Principles?
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- If Principle is Science, Design Patterns is applied Science - easy to relate to and understand
- Principles like Science is very vast in nature, Applied Science is very narrow in scope and easy to study
- Study Design Pattern and try to understand underlying principle behind it
- Mostly for design - OOP's Principles are good to understand design patterns
- Study of Craig Larman's work will also help
- Universal principles like - YAGNI, DRY, Rule of 3 also helps in understanding mindset of author of pattern
What is Code Smells?
Patterns to understand where is problem in coding
| Code Smell | Refactoring Pattern |
|---|---|
| Alternative Classes with Different Interfaces | Unify Interfaces with Adapter Rename Method Move Method |
| Combinatorial Explosion | Replace Implicit Language with Interpreter |
| Comments (a.k.a. Deodorant) | Rename Method Extract Method Introduce Assertion |
| Conditional Complexity | Introduce Null Object Move Establishment to Decorator Replace Condition Logic to Strategy Replace State Altering Condition with State |
| Data Class | Move Method Encapsulate Field Encapsulate Collection |
| Data Clumps | Extract Class Preserve Whole Object Introduce Parameter Object |
| Divergent Change | Extract Class |
| Feature Envy | Extract Method Move Method Move Field |
| Code Smell | Refactoring Pattern |
|---|---|
| Duplicate Code | Chain Constructors Extract Composite Extract Method Extract Class Form Template Method Introduce Null Object Introduce Polymorphic Creation with Factory Method Pull Up Method Pull Up Field Replace One/Many Distinctions with Composite Substitue Algorithm Unify Interfaces with Adapter |
| FreeLoader (Lazy Class) | Collapse Hierarchy Inline Class Inline Singleton |
| Inappropriate Intimacy | Move Method Move Field Change Bidirectional Association to Unidirectional Association Extract Class Hide Delegate Replace Inheritance with Delegation |
Thank You
Design Patterns
By Madhavrao Pachupate
Design Patterns
- 97
