You have completed all the necessary design patterns required while implementing your solution. However, it is not fixed that you must always use these design patterns exactly as defined. You can always tweak or adapt a pattern according to your own solution and requirements. The main goal of using design patterns is to make the code more maintainable, flexible, and understandable not to increase complexity unnecessarily.
- The first important principle is Keep It Simple, Stupid (KISS). Your goal should always be simplicity. Do not force yourself to use a design pattern just because you feel developers are expected to use them. If a simple solution solves the problem clearly and efficiently, then that solution is perfectly acceptable. Over-engineering a simple problem often makes the code harder to read and maintain.
- Another good practice is to apply a design pattern only when your current implementation no longer meets your needs. If the code becomes difficult to extend, maintain, or reuse, then it may be the right time to introduce a suitable pattern. Before applying any pattern, think about possible future scenarios and whether the pattern actually helps solve those problems.
- It is also important to understand the problem clearly before choosing any pattern. A design pattern is a tool, not a rule. Choosing a pattern without understanding the real problem can make the design unnecessarily complex. Always focus first on the requirements, then decide whether a pattern is truly needed.
- Another useful practice is to keep classes and methods small and focused. Each class should have a clear responsibility. When a class starts doing too many things, it becomes difficult to modify or test. Design patterns often help in separating responsibilities, but even without patterns, keeping code modular and organized is a good habit.
- You should also prefer readability over cleverness. Code is read more often than it is written. A straightforward implementation that everyone on the team can understand is usually better than a highly abstract design that only a few people understand.
- It is equally important to avoid premature abstraction. Do not generalize code too early. Write the simplest working solution first, and only introduce abstractions when you see repetition or a real need for flexibility. This approach keeps the design clean and prevents unnecessary layers.
- Another best practice is to document your intent when using a pattern. Even a short comment explaining why a pattern was used can help other developers understand the design decisions quickly.
Finally, remember that design patterns are guidelines, not strict rules. Real-world software often requires adapting or combining ideas rather than strictly following textbook implementations. The best design is the one that solves the problem clearly, remains easy to maintain, and can evolve with changing requirements.
Interview CheatSheet
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Strategy Pattern :
Trigger clue: “Different algorithms, interchangeable at runtime”
Core idea: Encapsulate algorithms and make them interchangeable so the behavior can be selected at runtime. -
Observer Pattern :
Trigger clue: “One-to-many dependency” or “Event notification system”
Core idea: When one object (Subject) changes state, all dependent objects (Observers) are notified automatically. -
Decorator Pattern :
Trigger clue: “Add behavior dynamically without modifying existing code”
Core idea: Wrap an object inside another object to extend behavior at runtime. -
Factory Method Pattern :
Trigger clue: “Defer object creation to subclasses”
Core idea: Define an interface for creating objects but let subclasses decide which class to instantiate. -
Abstract Factory Pattern :
Trigger clue: “Create families of related objects”
Core idea: Provide an interface to create related objects without specifying their concrete classes. -
Singleton Pattern :
Trigger clue: “Only one instance should exist”
Core idea: Ensure a class has only one instance and provide a global access point. -
Command Pattern :
Trigger clue: “Undo/Redo”, “Queue requests”, “Encapsulate actions”
Core idea: Encapsulate a request as an object to parameterize clients and support undo or logging. -
Adapter Pattern :
Trigger clue: “Incompatible interfaces must work together”
Core idea: Convert one interface into another expected by the client. -
Facade Pattern :
Trigger clue: “Provide a simple interface to a complex subsystem”
Core idea: Hide system complexity behind a single unified interface. -
Iterator Pattern :
Trigger clue: “Traverse a collection without exposing internal structure”
Core idea: Provide a standard way to access elements sequentially without revealing the underlying representation. -
Composite Pattern :
Trigger clue: “Tree structure” or “Treat individual and group uniformly”
Core idea: Compose objects into tree structures and treat individual objects and compositions uniformly. -
State Pattern :
Trigger clue: “Behavior changes based on internal state”
Core idea: Allow an object to change its behavior when its internal state changes. -
Proxy Pattern :
Trigger clue: “Control access to an object”
Core idea: Provide a surrogate or placeholder that controls access to another object. -
Compound Pattern :
Trigger clue: “Multiple patterns combined in one design”
Core idea: Combine several design patterns to solve a complex problem in a structured way.