Result type for functional error handling in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Result type in Kotlin?

The Result type is used to represent the outcome of an operation that can either succeed with a value or fail with an exception, enabling functional error handling without throwing exceptions.

beginner

How do you create a successful Result in Kotlin?

You create a successful Result by using Result.success(value), where value is the successful result you want to wrap.

beginner

How do you create a failed Result in Kotlin?

You create a failed Result by using Result.failure(exception), where exception is the error you want to represent.

intermediate

What does the getOrElse function do when called on a Result?

The getOrElse function returns the successful value if present; otherwise, it returns a default value provided by a lambda function.

intermediate

How can you handle both success and failure cases of a Result in Kotlin?

You can use the fold function, which takes two lambdas: one for handling success and one for handling failure, allowing you to process both outcomes cleanly.

Which function creates a successful Result in Kotlin?

A Result.error(value)

B Result.failure(value)

C Result.success(value)

D Result.ok(value)

Use Result.success(value) to create a successful result wrapping the value.

What does Result.failure(exception) represent?

A A successful result with an exception

B A failed result with an exception

C A successful result with a null value

D An ignored error

Result.failure(exception) represents a failure wrapping the given exception.

Which method returns the value inside a Result or a default if it failed?

A getOrElse()

B getOrNull()

C fold()

D onSuccess()

getOrElse() returns the success value or a default if the result is failure.

How can you run code only when a Result is successful?

A getOrElse { }

B onFailure { }

C fold { }

D onSuccess { }

onSuccess { } runs the given block only if the result is successful.

What does the fold function do on a Result?

A Processes success and failure with two lambdas

B Runs a block only on failure

C Returns the success value or throws an exception

D Converts the result to a nullable type

fold takes two lambdas to handle success and failure cases separately.

Explain how the Kotlin Result type helps with functional error handling.

Think about how you can handle errors without try-catch blocks.

Describe how to use fold with a Result to handle both success and failure.

Consider how you can write one expression to handle both outcomes.