A design pattern is a reusable solution to a commonly occurring problem in software design. It is not a piece of code that you copy-paste, but rather a general template or guideline for solving a particular type of problem in a flexible and maintainable way.
Think of it like an architect’s blueprint — it doesn’t build the house for you, but it gives you a structured way to build one efficiently and correctly.
Key Points:
- Not code, but a concept – A design pattern describes how to structure classes, objects, or interactions to solve a recurring design problem.
- Reusable – Patterns can be applied across multiple projects and situations.
- Best practices – They represent the collected wisdom of experienced developers.
- Language-independent – You can use the same pattern in Java, PHP, Python, or C#, though the implementation details may differ.
Types of Design Patterns
Design patterns are generally divided into three categories (as popularized by the “Gang of Four” book):
- Creational Patterns (object creation)
- Examples: Singleton, Factory, Builder, Prototype
- Structural Patterns (object composition/relationships)
- Examples: Adapter, Decorator, Composite, Proxy
- Behavioral Patterns (object interaction/communication)
- Examples: Observer, Strategy, Command, Iterator
Example:
Suppose you want only one instance of a database connection across your application. Instead of creating new objects everywhere, you can use the Singleton Pattern to ensure only one shared instance is used.
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