内聚、耦合与关注点分离
掌握决定代码是否易于维护的三个基础软件设计特性：高内聚、低耦合和清晰的关注点分离
内聚、耦合与关注点分离 是 CoddyKit 上的免费 Clean Architecture & Design Patterns in Practice 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Clean Architecture & Design Patterns in Practice 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Clean Architecture & Design Patterns in Practice 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Why These Properties Matter
Under clean code and SOLID lie three deeper design properties: cohesion, coupling, and separation of concerns. They explain why the rules work.
What is Cohesion
Cohesion measures how well a module’s responsibilities belong together. High cohesion = one well-defined job; low cohesion = a grab-bag of unrelated methods.
Low vs High Cohesion
Compare the two: the Util class mixes unrelated concerns, while UserRepository is tightly focused. That focus is high cohesion.
// Low cohesion
class Util {
saveUser() {}
sendEmail() {}
formatDate() {}
}
// High cohesion
class UserRepository {
save() {}
findById() {}
}What is Coupling
Coupling measures how much one module depends on another’s internals. Tight coupling spreads changes everywhere; loose coupling keeps interactions minimal.
Tight Coupling Example
Here OrderService creates its own SmtpMailer, locking it to that exact class. Swapping the mailer means editing the service — tight coupling.
class OrderService {
constructor() {
this.mailer = new SmtpMailer();
}
}Loosening the Coupling
Inject the mailer instead. Now OrderService depends on an abstraction and accepts any implementation. That’s loose coupling.
class OrderService {
constructor(mailer) {
this.mailer = mailer;
}
}The Sweet Spot
The sweet spot is high cohesion and low coupling together: focused modules that stay independent, so systems are easy to change, test, and reason about.
Separation of Concerns
Separation of concerns means splitting a program so each part owns one distinct concern — keep UI, business logic, and data access in separate layers.
Mixed Concerns
This function tangles data access, logic, and presentation together. Touch any one concern and you risk breaking the others — mixed concerns.
function showTotal(id) {
const rows = db.query('SELECT * FROM orders WHERE id=' + id);
const total = rows.reduce((s, r) => s + r.price, 0);
document.body.innerHTML = 'Total: ' + total;
}Separated Concerns
Split it into a repository, a calculator, and a view. Each concern now changes and tests independently. Much cleaner.
const order = repository.findById(id);
const total = calculator.total(order);
view.render(total);How They Connect to SOLID
These properties underpin SOLID: single responsibility drives cohesion, dependency inversion drives low coupling, and layering expresses separation of concerns.
Quick Check
High cohesion, low coupling — can you tell them apart?
Recap
You’ve got the foundations: cohesion keeps related work together, low coupling minimizes dependencies, and separation of concerns divides by purpose.
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常见问题解答
「内聚、耦合与关注点分离」课时是免费的吗？
是的 — 「内聚、耦合与关注点分离」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Clean Architecture & Design Patterns in Practice 课程的其余内容，请升级到 CoddyKit PRO。 Clean Architecture & Design Patterns in Practice 课程共包含 4 节课。
「内聚、耦合与关注点分离」这节课中我会学到什么？
掌握决定代码是否易于维护的三个基础软件设计特性：高内聚、低耦合和清晰的关注点分离 你通过在浏览器中直接运行的动手代码来练习 Clean Architecture & Design Patterns in Practice，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Clean Architecture & Design Patterns in Practice 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Clean Architecture & Design Patterns in Practice 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「内聚、耦合与关注点分离」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Clean Architecture & Design Patterns in Practice 课中编写并运行代码吗？
能。每节 Clean Architecture & Design Patterns in Practice 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。
此课程中的所有课时
- 整洁代码简介
- SOLID 原则概览
- 良好设计的价值
- 内聚、耦合与关注点分离