例として、TypeScriptのコードを通して、これらの特徴を持つインターフェースを説明する。
まず、ユーザーデータを表す型を定義する。
User インターフェースはユーザーデータの構造を明確にし、明確な抽象化と一貫性を示す。
ここでは、登録するためのユーザーに必要な情報は、idと名前、メールアドレスという最小限に絞っている。
Enhance Your Design Skills by Understanding Interfaces
Episode 3: Principles of Interface Design
(Last updated: 2024.11.14)
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This article takes about 5 minutes to read!
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"What Makes a Good Interface?"
In the previous episodes, we explored the overview, roles, and practical usage of interfaces. In this article, we’ll dive into the principles necessary for designing better interfaces. Designing good interfaces can significantly improve software quality and development productivity. By the end of this article, we hope you’ll be able to design safe, understandable, and flexible interfaces with great extensibility.
[Table of Contents]
Characteristics of a Good Interface
Principles of Interface Design
Summary
1. Characteristics of a Good Interface
The characteristics of a good interface can be summarized in the following six points:
■ Clarity and Simplicity
A good interface is simple enough for users to understand intuitively. It minimizes complexity and provides only the necessary functionality to achieve its purpose.
■ Consistency
Using consistent patterns and designs allows users to easily predict how the interface behaves. Following existing standards and conventions helps new users quickly grasp and use the interface.
■ Flexibility
A well-designed interface accommodates future changes and extensions. Ideally, it should be customizable to meet different user needs.
■ Loose Coupling
Interfaces should minimize dependencies between modules. Components should be easily replaceable with other implementations.
■ Practicality
Interfaces must include functions users truly need. With the four qualities above, they naturally improve user efficiency.
■ Documentation and Support
Comprehensive, easy-to-understand documentation helps users fully utilize the features. Timely support and active communities or forums enable knowledge sharing among users.
These principles affect both the user experience and the overall quality of the software. By understanding clarity, consistency, flexibility, loose coupling, practicality, and support, you can learn practical interface design approaches.
Additionally, good interface design requires smooth communication within the organization—don’t overlook this essential point.
Communication is key to designing good interfaces
2. Principles of Interface Design
Interface design should prioritize consistent design and behavior. This means similar functions and components behave in the same way. Simplicity is maintained by providing only the necessary features and eliminating extras, focusing on the core functionalities users need. Good interface design abstracts away technical complexities to present a more intuitive experience for users.
Furthermore, an interface should be adaptable to future changes or extensions, making it easier to add or modify features later. Minimizing dependencies between components is also vital—interfaces should operate independently from the systems or components they interact with. Lastly, safety must be ensured. Interfaces should clearly report errors and provide mechanisms for safe operations.
Let's look at how these qualities appear in TypeScript code. First, we define a type to represent user data. The `User` interface clarifies the structure of user data and provides clear abstraction and consistency. It defines only the essential elements needed for user registration: ID, name, and email.
Interface representing user data type
Next, we define the interface for services that handle user-related operations. Each method follows a consistent format and only provides minimal, necessary operations. If new operations are needed, we can easily extend `IUserService` by adding new methods. The `UserService` class depends on `IUserService`, remaining decoupled from specific implementations. This achieves simplicity, extensibility, and loose coupling. The code defines CRUD methods: `getUser`, `addUser`, `updateUser`, and `deleteUser`.
Interface for user-related operations
Finally, we show a sample class that implements the above interface. Actual behavior and logic are written here and can be modified later.
Example of class implementation
This example demonstrates how the characteristics of good interface design can be expressed in code. Even for simple CRUD functions, such a structure can be adapted for various uses. This kind of design improves maintainability, extensibility, and reusability of the system.
3. Summary
In this article, we covered the role of interfaces and showed practical implementation examples. Interfaces don’t contain behavior logic. When designing interfaces, aim for a minimal yet sufficient structure while keeping future extensibility in mind. Also, name properties and methods clearly, and avoid overlapping roles with other interfaces.
If you can define minimal, scalable interfaces with future implementation in mind, your code will be easier to maintain, extend, and reuse.
▼References
“Extraordinary Software Design Intro – Understanding Object-Oriented Programming with PHP” by Hisateru Tanaka, Gijutsu-Hyoronsha
How to Design Classes: Ideas and Tips for Class Design by Deep Rain
