README.md

Kotlin Result Extension

This project adds several new methods to the Kotlin Result type to facilitate more robust, functional-style error handling. The main focus is on chaining Result operations together and handling more complex and nested structures.

New Functions

flatMap

Transforms the value of a successful Result and expects the result of the transformation to return a Result. Using just map, this leads to Result<Result<T>>, but flatMap will unwrap the outer Result so only the inner one is returned.

val doMoreReturnResult = { value -> "More: $value" }

val result = runCatching {
	"Start Value"
}
	.flatMap { startValue -> doMoreReturnResult(startValue) }
	.getOrThrow()

// "result" is "More: Start Value"

flatten

A simple way to unwrap nested Results from chained operations.

val doMoreReturnResult = { value -> "More: $value" }

val result = runCatching {
	"Start Value"
}
	.map { startValue -> doMoreReturnResult(startValue) }
	.flatten()
	.getOrThrow()

// "result" is "More: Start Value"

flatRecover

Similar to the existing recover function, only it expects a Result to be returned from the transformation. Like the others, it will unwrap the Result to propagate it. Useful for recovering with operations that return a result.

val result = runCatching { throw RuntimeException("Dying") }
    .flatRecover { Result.success("Hello World") }
    .getOrThrow()
// "result" is "Hello World"

recoverCatchingAndFlatten

Same as flatRecover, but it can handle exceptions being thrown within the function body.

val result = runCatching { throw RuntimeException("Dying") }
    .flatRecoverCatching { Result.success("Hello World") }
    .getOrThrow()
// "result" is "Hello World"