Clean Code

Заметки из книги Чистый код

Чистый код - может читать и улучшать любой разработчик. Улучшает читаемость, изменяемость, расширяемость и поддерживаемость.

Основные разделы

• General rules
• Design rules
• Understandability tips
• Names rules
• Functions rules
• Comments rules
• Source code structure
• Objects and data structures
• Tests
• Code smells

General rules

• Придерживайтесь конвенциям.
• KISS(Keep it simple stupid).
• DRY(Don’t Repeat Yourself).
• Правило бойскаута. Оставляйте код чище, чем он был до вас.
• Всегда ищите первопричину проблемы.

Design rules

• Keep configurable data at high levels.
• Prefer polymorphism to if/else or switch/case.
• Separate multi-threading code.
• Prevent over-configurability.
• Use dependency injection.
• Follow Law of Demeter. A class should know only its direct dependencies.

Understandability tips

• Be consistent. If you do something a certain way, do all similar things in the same way.
• Use explanatory variables.
• Encapsulate boundary conditions. Boundary conditions are hard to keep track of. Put the processing for them in one place.
• Prefer dedicated value objects to primitive type.
• Avoid logical dependency. Don't write methods which works correctly depending on something else in the same class.
• Avoid negative conditionals.

Names rules

• Используй осмысленные, говорящие имена.
• Используйте произносимые имена.
• Используйте имена, доступные для поиска.
• Избегай магических чисел и строк.

Functions rules

• Предпочитай ранние return вместо глубокой вложенности.

if (user == null) return;
if (!user.isActive()) return;
process(user);
            

• Делай функции маленькими и сфокусированными.
• Do one thing.
• Use descriptive names.
• Избегай длинных списков параметров. Лучше объекты содержащие эти параметры.
• Have no side effects.
• Don't use flag arguments. Split method into several independent methods that can be called from the client without the flag.

Comments rules

• Комментарии должны ответать на вопрос Почему?, а не Что?
• Always try to explain yourself in code.
• Don't be redundant.
• Комментируй только там, где это действительно необходимо.
• Don't use closing brace comments.
• Don't comment out code. Just remove.
• Use as explanation of intent.
• Use as clarification of code.
• Use as warning of consequences.
• Пиши хорошие сообщения к коммитам.

Source code structure

• Separate concepts vertically.
• Related code should appear vertically dense.
• Declare variables close to their usage.
• Dependent functions should be close.
• Similar functions should be close.
• Place functions in the downward direction.
• Keep lines short.
• Don't use horizontal alignment.
• Use white space to associate related things and disassociate weakly related.
• Don't break indentation.

Objects and data structures

• Прячь внутренние структуры.
• Prefer data structures.
• Avoid hybrids structures (half object and half data).
• Should be small.
• Do one thing.
• Small number of instance variables.
• Base class should know nothing about their derivatives.
• Better to have many functions than to pass some code into a function to select a behavior.
• Prefer non-static methods to static methods.

Tests

• One assert per test.
• Readable.
• Fast.
• Independent.
• Repeatable.

Code smells

• Rigidity. The software is difficult to change. A small change causes a cascade of subsequent changes.
• Fragility. The software breaks in many places due to a single change.
• Immobility. You cannot reuse parts of the code in other projects because of involved risks and high effort.
• Needless Complexity.
• Needless Repetition.
• Opacity. The code is hard to understand.