Basics of refactoring a bad code | part 1 - If condition

#designprinciples #codingstandards

We have all been in a situation that when we are growing as a developer often we find ourselves writing code that doesn't look right or we have a doubt that whether it follows the best practices. This article is just part 1 of the total n series. (I really don't know how many would come 🤷‍♂️)

If statement

If statements can be a root cause of writing bad code. Always think twice before writing nested if conditions whether there is a way to simplify it. A badly written if condition can reduce the readability of the program.
Let's make the following assumptions here. Any clean code will have the following properties.

Readable
Concise
Scalable - Should be able to allow more conditions or business logic to be added without affecting the above two factors.

Example 1 of Bad code

	// Not clear code
	// Readable - 0
	// Concise - 0
	// Scalable - 0
	fun isUserValid(user: User): Boolean {
	if (user.token != null) {
	if (user.token != "") {
	if (user.userId != null) {
	if (user.userId != "") {
	return true
	}
	}
	}
	}
	return false
	}

view raw art_bad_if_statement.kt hosted with ❤ by GitHub

Improvement 1 - Combining relevant conditions

	// Slightly improved
	// Readable - 1
	// Concise - 1
	// Scalable - 0
	fun isUserValid(user: User): Boolean {
	if(user.token != null && user.token != "") {
	if(user.userId != null && user.userId != "") {
	return true
	}
	}
	return false
	}

view raw art_imp_if_statement.kt hosted with ❤ by GitHub

Improvement 2 - Applying inversion of condition

	// Much better
	// Readable - 1
	// Concise - 1
	// Scalable - 1
	fun isUserValid(user: User): Boolean {
	if(user.token == null \|\| user.token == "") {
	return false
	}
	if(user.userId == null \|\| user.userId == "") {
	return false
	}
	// More complex conditions
	return true
	}

view raw art_imp_2_if_statement.kt hosted with ❤ by GitHub

Combining relevant conditions

Combining multiple conditions that are relevant by using the logical operator can reduce down the lines of code and implies a better understanding of the condition.

Inversion of condition

Just by inverting the thought process that goes for the condition in if statement can vastly improve the readability.

Example 2 of Bad code

	// Bad code
	// Readable - 1
	// Concise - 0
	// Scalable - 0
	fun unlockPremiumFeature(user: User): Boolean {
	if(isUserValid(user)) {
	if(isPremiumUser(user)) {
	// Unlock premium membership
	} else {
	// Activate Premium membership
	// Unlock premium feature
	}
	return true
	} else {
	return false
	}
	}

view raw art_bad_if_statement2.kt hosted with ❤ by GitHub

Improved Code - Applied short-circuiting + inversion of condition

	//Improved If statement
	// Readable - 1
	// Concise - 1
	// Scalable - 1
	fun unlockPremiumFeature(user: User): Boolean {
	// Inversion of condition + short-circuiting
	if(!isUserValid(user)) {
	return false
	}
	if(!isPremiumUser()) {
	// Unlock premium membership
	}
	// Unlock premium feature
	return true
	}