When I prefer use when then if-else in Kotlin

TL;DR

• if-else for simple cases with only one conditions or to use early returns pattern.
• when for more complex cases with multiple conditions and to have a cleaner code.

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Ever feel lost in a maze of if-else statements, desperately trying to handle every input nuance? Fear not, fellow dev! Kotlin's when statement offers a sleek and powerful escape route.
Forget the Java switch cases or the endless else if that makes your code's readability horrible. when can simplify your logic, writing multiple conditions into a single and clear block.

Why when is better in my option?

• Clean Code: allows you to write more concise and readable code, especially when you need to check multiple conditions.

• Type Safe: runtime mistakes can be avoided by checking the expression against each case value.

• Extensibility: can be easily extended to handle new cases.

Code example

fun renderRequests(userId: String) = renderComponent {
  val user = getUser(userId)
    when (user.role) {
      is ROLE.CHILD -> return
      is ROLE.UNCLE -> defaultRequestError()
      is ROLE.PARENT -> {
        buildRenderComponent(user)
      }
    }
}

Now compare with if-else:

fun renderRequests(userId: String) = renderComponent {
  val user = getUser(userId)
   if (user.role == ROLE.CHILD) {
    return
   } else if (user.role == ROLE.UNCLE) {
    defaultRequestError()
   } else if (user.role == ROLE.PARENT) {
    buildRenderComponent(user)
   }
}

When if-else is a better option?

When I want to use early returns pattern.

Writing functions or methods, early return means that the expected positive result is returned at the end of the function, and when conditions are not met, the rest of the code ends the execution by returning or throwing an exception.

Code example

fun sayMyName(name: String): String {
 if (!name || name.length < 0) {
    return;
  }
  return `Hello, ${name}`
}

References

• Kotlin documentation on control flow
• Baeldung tutorial on when
• Kotlin: An Illustrated Guide • Chapter 3 - Kotlin Conditionals: When and If