How do you manage errors in Kotlin?

1 Types of errors

There are two main types of errors in Kotlin: compile-time errors and run-time errors. Compile-time errors are detected by the compiler before the program runs, and they usually indicate syntax, logic, or type errors. For example, if you try to assign a string value to an integer variable, you will get a compile-time error. Run-time errors are not detected by the compiler, but they occur during the execution of the program, and they usually indicate exceptions, assertions, or external factors. For example, if you try to access a null value or an invalid index, you will get a run-time error.

2 Handling exceptions

Exceptions are a common type of run-time error that represent exceptional or abnormal situations that disrupt the normal flow of the program. For example, an IOException occurs when there is a problem with input or output operations, such as reading or writing a file. To handle exceptions in Kotlin, you can use the try-catch-finally block, which allows you to execute some code in the try block, catch and handle any exceptions that occur in the catch block, and optionally execute some code in the finally block regardless of whether an exception occurred or not. For example:

try {
  // some code that may throw an exception
} catch (e: IOException) {
  // handle IOException
} catch (e: Exception) {
  // handle any other exception
} finally {
  // some code that always executes
}        

3 Using nullability

Nullability is a feature of Kotlin that allows you to explicitly declare whether a variable or a type can hold a null value or not. Null values can cause NullPointerExceptions, which are run-time errors that occur when you try to access or use a null value as if it were not null. To avoid this, you can use the nullable type notation, which adds a question mark (?) after the type name, to indicate that a variable or a type can be null. For example:

var name: String? = null // name can be null
var age: Int = 25 // age cannot be null        

To safely access or use a nullable value, you can use the null-safe operator (?.), which checks if the value is null before accessing or using it, and returns null if it is. For example: name?.length // returns null if name is null, otherwise returns name's length You can also use the Elvis operator (?:), which provides a default value if the value is null. For example: val length = name?.length ?: 0 // returns 0 if name is null, otherwise returns name's length

4 Testing assertions

Assertions are statements that check if a condition is true or false, and throw an AssertionError if it is false. Assertions are useful for testing and debugging purposes, as they can help you verify the correctness of your code and catch potential errors early. To use assertions in Kotlin, you can use the assert() function, which takes a boolean expression and an optional message as arguments. For example: assert(age > 0) { "Age must be positive" } // throws an AssertionError if age is not positive However, assertions are only enabled when the JVM is run with the -ea option, which means they are not active by default. Therefore, you should not rely on assertions for error handling in production code, as they may not be executed at all.

5 Following best practices

Using the built-in features of Kotlin to manage errors is important, but you should also follow some general best practices to write robust and reliable code. Start by giving descriptive and meaningful names to your variables, functions, and classes, and use comments and documentation to explain complex or unclear code. Additionally, use consistent and appropriate coding style and conventions, avoid using magic numbers or hard-coded values, break down nested or complex expressions into smaller ones, use exceptions only for exceptional or abnormal situations, handle exceptions close to their source with useful messages, and test your code thoroughly and frequently. Doing so will make your code more organized, maintainable, flexible, adaptable, readable, testable, efficient, predictable, modular, and user-friendly.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?