Design principles and OOP
Build a practical understanding of design principles and oop from the underlying principles.
DESIGN · 71 ARTICLES
Software Design
Good design begins with reducing the cost of change. Connect object-oriented principles, design patterns, dependencies, and modularization into one practical flow.
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Design patterns
Build a practical understanding of design patterns from the underlying principles.
Dependency design
Build a practical understanding of dependency design from the underlying principles.
Modularization
Build a practical understanding of modularization from the underlying principles.
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[SOLID #1] SOLID in Five Letters: Understand It Instead of Memorizing It (SRP · OCP · LSP)
You have probably been asked at least once in an interview, “Could you explain the SOLID principles?”
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Why Design Patterns Matter—and Why Not to Trust Them Blindly
The question “Do we still need to study design patterns?” comes up regularly in developer communities.
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[Modularization #1] What Is Modularization? Why Split Code? (Cohesion & Coupling)
As projects grow, changing one file becomes increasingly intimidating. It is hard to tell how far the impact will spread.
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Swift DI Library Factory: Summary and Differences from Swinject
Factory is a Swift DI library that catches missing dependency registrations at compile time. As of July 2026, this guide covers version 3.3.1, basic usage, scope declarations, test and preview injection, and differences from Swinject.
Read articlePremature optimization is the root of all evil: what Knuth really meant
Knuth’s statement that “premature optimization is the root of all evil” is a truncated quote. This article explains the original context—forget the 97% and focus on the 3%—and the practical rule of optimizing after confirming bottlenecks with a profiler.
Read articleProtocol-Oriented Programming (POP): Going Beyond OOP's Limits
Protocol-oriented programming (POP) designs types around what they can do, not what they inherit. This article covers where inheritance falls short, how to solve it by composing protocols, and when to avoid it, with Swift examples.
Read articleMediator vs. Observer vs. Facade: 3 object communication patterns
Mediator coordinates tangled object relationships centrally, Observer broadcasts state changes one-to-many, and Facade wraps complex internals behind a simple entry point. Compare the three patterns and selection criteria with Swift examples.
Read articleDI, IoC, and DIP: a complete guide to the differences
DI, IoC, and DIP are concepts at different levels. DIP is the principle that determines what to depend on, IoC is about who holds control, and DI is the technique of supplying dependencies. This guide covers the distinctions with examples and interview answers.
Read articleThe Essence of OOP Is Messaging: Alan Kay’s Real OOP
When studying OOP, we always start by memorizing inheritance, encapsulation, and polymorphism.
Read articleCommand vs Memento: Two Approaches to Implementing Undo
Have you ever gotten stuck trying to build an undo feature yourself?
Read articleWhy Swift’s final Keyword Belongs on Classes (Performance & Design Summary)
You’ve probably heard someone say in a code review, “Please add final to this class.”
Read articleStrategy vs Template Method vs Command: Differences
Have you ever had this moment while studying design patterns?
Read articleOOP Abstraction and Encapsulation: If You Always Confuse Them, This Article Ends It
When studying object-oriented programming (OOP), you inevitably encounter a major stumbling block.
Read articleFactory Method vs. Abstract Factory
The GoF Factory Method delegates the decision of an object's concrete type to subclasses, while Abstract Factory creates families of related products together. This article compares their intent and selection criteria with Swift examples.
Read articleWhen to Adopt a DI Container? A Complete Guide to Introducing Swinject and Factory
At some point while developing for iOS, this question comes up.
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