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In software development projects, class diagrams are like blueprints when explaining the structure of complex systems. However, these blueprints alone can sometimes make it difficult to understand how the system actually operates at a specific moment. This is where UML Object Diagrams become incredibly useful—they provide a snapshot of the system at a particular point in time. In this article, we’ll explore what UML Object Diagrams are, what their main components consist of, and how they differ from class diagrams so that you’ll clearly understand when to use them. We’ll also look at examples applied to real-world development scenarios and best practices to help enhance your software design skills.

Software development is the process of building complex systems. Often, multiple developers collaborate, and there's a need to grasp the structure of the system at a glance. What if there were a tool to visually express the system with a unified set of conventions? That’s where UML (Unified Modeling Language) comes in. UML is a standard modeling language used to visualize, specify, and document object-oriented software systems. Especially as microservice architecture and large-scale system design become more common, UML’s importance continues to grow. Among the many types of UML diagrams, the Class Diagram stands out as a core tool that clearly shows the static structure of a system. In this post, we’ll walk through the basic concepts, components, and real-world uses of class diagrams. This guide will help you better understand system structure and communicate more effectively with your team.

클래스, 시퀀스, 유스케이스 등 주요 UML 다이어그램 종류를 실무 예제와 함께 알아보세요. 소프트웨어 설계 능력을 한 단계 업그레이드하세요. 소프트웨어 개발에서 복잡한 시스템을 설계할 때, 팀원들과 명확하게 소통하는 것은 필수입니다. 코드로 바로 구현하기 전에 시스템의 구조와 동작 방식을 시각화할 수 있다면 어떨까요? 바로 이 지점에서 UML(Unified Modeling Language)이 그 역할을 수행합니다. UML은 객체 지향 소프트웨어 시스템을 시각화, 명세화, 구축, 문서화하기 위한 표준 모델링 언어입니다. 1990년대 중반에 등장한 이후, UML은 소프트웨어 엔지니어링의 핵심 도구로 자리 잡았습니다. 특히 마이크로서비스 아키텍처나 대규모 시스템 설계가 일상화된 지금, UML의 중요성은 더욱 커지고 있어요. UML은 크게 구조적 다이어그램(Structural Diagrams) 과 행위적 다이어그램(Behavioral Diagrams) 으로 나뉩니다. 각 다이어그램은 시스템의 특정 측면을 표현하는 데 최적화되어 있죠. 이 글에서는 실무에서 자주 사용되는 UML 다이어그램 종류를 상세히 살펴보고, 각 다이어그램이 어떤 상황에서 유용한지 실제 예시와 함께 알아보겠습니다.

When developing APIs with NestJS, you often need to validate parameters in the MongoDB ObjectId format. If an invalid ID format is passed, it results in a database query error and an unfriendly error message to the user. Using the @IsMongoId() decorator from class-validator makes this easy to handle. Just add this decorator to a DTO, and MongoDB ObjectId validation happens automatically. Invalid requests are blocked before reaching the controller. In this post, we’ll cover everything from basic usage of @IsMongoId() to its internal implementation, real-world usage, and even creating custom validations.

In NestJS, class-validator is a powerful tool that simplifies data validation. By adding a few decorators to a DTO (Data Transfer Object), you can easily control the structure of incoming requests. However, sometimes decorators behave differently than expected, causing confusion. One such decorator is @IsDecimal. Have you ever encountered an error saying "not a valid decimal" even though you sent a properly formatted decimal number? In this post, I’ll clearly explain why @IsDecimal behaves this way and how to properly validate decimal numbers in NestJS.

When validating DTOs in NestJS, there are many cases where you need to "allow only specific values". For example, you may want to allow only 'admin' | 'user' | 'blogger' for the role (role) or 'S' | 'M' | 'L' | 'XL' for product size (size). In such cases, using the @IsEnum decorator from class-validator effectively allows for clean and secure input validation.

When developing with Next.js, how do you validate the data that comes through API routes or forms? Unlike frameworks like Express or NestJS, Next.js doesn't provide a built-in validation layer. This means developers have to write their own code to ensure data integrity. In this post, I’ll show you how to integrate the familiar class-validator library—popular among NestJS developers—into a Next.js project. Step by step, we'll explore how you can write cleaner, more maintainable, and reliable validation logic using decorator-based validation. From my personal experience, introducing class-validator significantly improved both the stability of the product and the ease of development. While Next.js isn’t the most convenient tool for building APIs, a well-designed architecture can still make it a capable API server framework. This article is based on Next.js version 15. Please keep that in mind. 😉

When working with TypeScript, there are times when you want to write reusable code that can handle various types. This is exactly when generics come into play. And when used with the keyof operator, you can safely work with object properties. In this post, we'll explore how to use TypeScript generics along with keyof, with practical examples. From basic concepts to immediately applicable patterns, the content is structured to build your understanding step-by-step.

When developing backend systems that require complex business logic and high performance, the traditional CRUD pattern often shows its limitations. In such cases, the CQRS (Command Query Responsibility Segregation) pattern can be a viable solution. This guide will walk you through implementing the CQRS pattern in NestJS step-by-step and share practical insights for applying it in real-world projects. From the core concepts of the CQRS pattern to its actual implementation and testing strategies in NestJS, this guide covers everything comprehensively to help you elevate your application architecture.

When developing a backend with NestJS, it can be confusing to decide when to use middleware and when to use interceptors. Both features allow you to insert logic between a request and a response, but they differ in timing and capabilities. In this post, we'll clarify the differences between middleware and interceptors based on NestJS’s request lifecycle, and examine which to use in real-world scenarios.

When developing in JavaScript, you often need to copy objects. However, simply copying with the = operator can lead to unexpected bugs—because objects are reference types. In this post, we’ll explore the differences between shallow and deep copies, when to use each, and practical implementation methods you can apply immediately.

As a web developer, you’ll likely encounter situations where implementing 3D graphics or complex visualizations is necessary. While WebGL has been the standard for high-performance graphics on the web, a new option called WebGPU has now emerged. This article analyzes the key differences between WebGL and WebGPU, examining their strengths and weaknesses. It also offers a practical guide on which technology to choose in real-world development.