Code Quality Guide

클린 코드 원칙

1. 의미 있는 이름

# Bad
d = get_current_date()
arr = filter(u -> u.a > 18, users)

# Good
currentDate = get_current_date()
adultUsers = filter(user -> user.age > 18, users)

2. 함수는 작게, 한 가지 일만

# Bad: function doing multiple things
function processUser(user):
    # validation
    if not user.email:
        throw Error("Email required")
    # data transformation
    user.email = lowercase(user.email)
    # DB save
    db.users.insert(user)
    # send email
    sendWelcomeEmail(user)

# Good: single responsibility
function createUser(userData):
    validatedData = validateUserData(userData)
    normalizedData = normalizeUserData(validatedData)
    user = saveUser(normalizedData)
    sendWelcomeEmail(user)
    return user

3. 주석보다 코드로 표현

# Bad: explaining with comment
# check if adult
if user.age >= 18:
    ...

# Good: explain with function name
if isAdult(user):
    ...

function isAdult(user):
    ADULT_AGE = 18
    return user.age >= ADULT_AGE

4. 에러 처리

# Bad: ignoring error
try:
    doSomething()
catch error:
    pass  # do nothing

# Good: proper error handling
try:
    doSomething()
catch error:
    logger.error("Operation failed", error, context)
    throw ApplicationError("Failed to complete operation", error)

SOLID 원칙

Single Responsibility (단일 책임)

# Bad: multiple responsibilities
class UserService:
    createUser()
    sendEmail()
    generateReport()

# Good: single responsibility
class UserService:
    createUser()

class EmailService:
    sendEmail()

class ReportService:
    generateReport()

Open/Closed (개방/폐쇄)

# Bad: open for modification
function calculateArea(shape):
    if shape.type == "circle":
        return PI * shape.radius ^ 2
    else if shape.type == "rectangle":
        return shape.width * shape.height
    # need to modify function for new shapes

# Good: open for extension
interface Shape:
    calculateArea()

class Circle implements Shape:
    calculateArea():
        return PI * self.radius ^ 2

class Rectangle implements Shape:
    calculateArea():
        return self.width * self.height

리팩토링 패턴

Extract Method

# Before
function printReport(user):
    print("=" * 40)
    print("Name: " + user.name)
    print("Email: " + user.email)
    print("=" * 40)

# After
function printReport(user):
    printSeparator()
    printUserDetails(user)
    printSeparator()

function printSeparator():
    print("=" * 40)

function printUserDetails(user):
    print("Name: " + user.name)
    print("Email: " + user.email)

Replace Conditional with Polymorphism

# Before
function getSpeed(vehicle):
    switch vehicle.type:
        case "car": return vehicle.baseSpeed * 1.2
        case "bike": return vehicle.baseSpeed * 0.8
        default: return vehicle.baseSpeed

# After
class Vehicle:
    getSpeed(): return self.baseSpeed

class Car extends Vehicle:
    getSpeed(): return self.baseSpeed * 1.2

class Bike extends Vehicle:
    getSpeed(): return self.baseSpeed * 0.8

Guard Clause

# Before: nested conditionals
function processOrder(order):
    if order:
        if length(order.items) > 0:
            if order.status == "pending":
                # process logic

# After: Guard Clause
function processOrder(order):
    if not order: return
    if length(order.items) == 0: return
    if order.status != "pending": return
    
    # process logic

코드 스멜 (Code Smells)

탐지해야 할 패턴

예시

# Magic Numbers (Bad)
if user.age >= 18 and length(items) <= 10:
    ...

# Named Constants (Good)
ADULT_AGE = 18
MAX_CART_ITEMS = 10

if user.age >= ADULT_AGE and length(items) <= MAX_CART_ITEMS:
    ...

코드 리뷰 체크리스트

• 코드가 읽기 쉬운가?
• 함수가 한 가지 일만 하는가?
• 이름이 의도를 명확히 드러내는가?
• 중복 코드가 있는가?
• 에러 처리가 적절한가?
• 테스트가 있는가?
• 성능 이슈가 있는가?
• 보안 취약점이 있는가?

관련 스킬

• testing: 테스트 작성 전략
• debugging: 에러 추적 및 디버깅