Code Refracting

Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. Its heart is a series of small behavior preserving transformations.

Martin Fowler

Refactoring

In software engineering, it means "reorganizing the structure of the code without changing the results."

No function is added when refactoring.

Sometimes it's easier to write a new code than refactoring.

Goal

To improve the quality of code and to make software development and maintenance efficient, it is carried out with the following purposes:

Improved readability

• Software becomes easier to understand.
• It makes it easier for developers to collaborate.

Improved Maintenance

• The maintenance process is simplified.
• It can reduce potential bugs by eliminating code duplication.
• Structuring and modularity make it easier to add new features or fix bugs

When

Code Review: You can improve and improve quality while reviewing code with fellow developers.

Just before adding features: it's easy to add new features to existing code, so existing code can be refactored.

Bug Fix: Refactoring in the process of fixing bugs makes it easier to understand and fix bugs.

Regular maintenance: improves and optimizes code periodically.

Way

Replace hard-coded numbers with constants

• Before

if (temperature > 100) { // boiling point
    // Do something if temperature is above boiling
}

• After

val BOILING_POINT = 100
if (temperature > BOILING_POINT) {
     // Do something if temperature is above boiling
}

To remove duplicate code

• Before

fun process(user: User) {
    if (user.status == UserStatus.SPROUT) {
        println("======= ## ${user.status} ## =======")
        // ...
    } else if (user.status == UserStatus.ROSE) {
        println("======= && ${user.status} && =======")
        // ...
    } else if (user.status == UserStatus.TREE) {
        println("======= @@ ${user.status} @@ =======")
        // ...
    }
}

• After

fun process(user: User) {
    if (user.status == UserStatus.SPROUT) {
        printStatus(user.status, "#")
        // ...
    } else if (user.status == UserStatus.ROSE) {
        printStatus(user.status, "&")
        // ...
    } else if (user.status == UserStatus.TREE) {
        printStatus(user.status, "@")
        // ...
    }
}

private fun printStatus(status: UserStatus, decorate: String) {
    println("======= $decorate$decorate $status $decorate$decorate =======")
}

Use simple conditional statements like trisom operators (Kotlin does not have trisom operators)

• Before

var text: String
if (zipCode != null) {
    text = "$zipCode) $address"
} else {
    text = address
}

• After

val text = if (zipCode != null) "$zipCode) $address" else address

val text = zipCode?.let { "$zipCode) $address" } ?: address

For conditional statements with multiple conditions, when is sometimes better.

• Before

val agePeriod = if (age >= 65) "old age"
else if (age >= 45) "middle age"
else if (age >= 30) "midlife"
else if (age >= 19) "young adulthood"
else if (age >= 7) "boyhood"
else "one's"

• After

val agePeriod = when {
    age >= 65 -> "old age"
    age >= 45 -> "middle age"
    age >= 30 -> "midlife"
    age >= 19 -> "young adulthood"
    age >= 7 -> "boyhood"
    else -> "one's"
}

To isolate a long method

• Before

fun process() {
    // Logic for validation
    // ...
    // Logic for calculations
    // ...
    // Logic for state changes
    // ...
}

• After

fun process() {
    validation()
    caluration()
    changeState()
}

fun validation() {
    // Logic for validation
}
fun caluration() {
    // Logic for calculations
}
fun changeState() {
    // Logic for state changes
}

Use meaningful names (variable names, method names, etc.)

• Before

fun process(num: Int): Boolean {
    return if (num % 4 == 0) !(num % 400 != 0 && num % 100 == 0) else false
}

• After

fun checkLeapYear(year: Int): Boolean {
    return if (year % 4 == 0) !(year % 400 != 0 && year % 100 == 0) else false
}

https://www.techtarget.com/searchapparchitecture/definition/refactoring

https://dev.to/documatic/5-code-refactoring-techniques-to-improve-your-code-2lia

https://woogong80.tistory.com/213#google_vignette

https://velog.io/@rlrhs11/Code-Refactoring코드-리펙토링-이란

https://ikkison.tistory.com/82

https://jeongkyun-it.tistory.com/66

https://dmdwn3979.tistory.com/13

https://2minmin2.tistory.com/72

https://taes-k.github.io/2-where-when-refactoring.html