Add Result.recover(Function) and Result.onError(Consumer)

This commit is contained in:
Paul Campbell 2018-07-07 23:02:02 +01:00
parent c5247d7c14
commit 28564a2129
4 changed files with 89 additions and 2 deletions

View file

@ -80,6 +80,16 @@ class Err<T> implements Result<T> {
return this; return this;
} }
@Override
public Result<T> recover(final Function<Throwable, Result<T>> f) {
return f.apply(error);
}
@Override
public void onError(final Consumer<Throwable> errorConsumer) {
errorConsumer.accept(error);
}
@Override @Override
public boolean equals(final Object other) { public boolean equals(final Object other) {
return other instanceof Err && Objects.equals(error, ((Err) other).error); return other instanceof Err && Objects.equals(error, ((Err) other).error);

View file

@ -108,6 +108,7 @@ public interface Result<T> extends Functor<T, Result<?>> {
/** /**
* Swaps the inner Result of a Maybe, so that a Result is on the outside. * Swaps the inner Result of a Maybe, so that a Result is on the outside.
*
* @param maybeResult the Maybe the contains a Result * @param maybeResult the Maybe the contains a Result
* @param <T> the type of the value that may be in the Result * @param <T> the type of the value that may be in the Result
* @return a Result containing a Maybe, the value in the Maybe was the value in a successful Result within the * @return a Result containing a Maybe, the value in the Maybe was the value in a successful Result within the
@ -177,4 +178,22 @@ public interface Result<T> extends Functor<T, Result<?>> {
* @return this Result * @return this Result
*/ */
Result<T> peek(Consumer<T> consumer); Result<T> peek(Consumer<T> consumer);
/**
* Provide a way to attempt to recover from an error state.
*
* @param f the function to recover from the error
* @return a new Result, either a Success, or if recovery is not possible an other Err.
*/
Result<T> recover(Function<Throwable, Result<T>> f);
/**
* A handler for error states.
*
* <p>When this is an error then tne Consumer will be supplier with the error. When this is a success, then nothing
* happens.</p>
*
* @param errorConsumer the consumer to handle the error
*/
void onError(Consumer<Throwable> errorConsumer);
} }

View file

@ -84,6 +84,16 @@ class Success<T> implements Result<T> {
return this; return this;
} }
@Override
public Result<T> recover(final Function<Throwable, Result<T>> f) {
return this;
}
@Override
public void onError(final Consumer<Throwable> errorConsumer) {
// do nothing - this is not an error
}
@Override @Override
public boolean equals(final Object other) { public boolean equals(final Object other) {
return other instanceof Success && Objects.equals(value, ((Success) other).value); return other instanceof Success && Objects.equals(value, ((Success) other).value);

View file

@ -452,6 +452,54 @@ public class ResultTest implements WithAssertions {
assertThat(peeked).isSameAs(result); assertThat(peeked).isSameAs(result);
} }
@Test public void success_whenOnError_thenIgnore() {
//given
final Result<Integer> ok = Result.ok(1);
//when
ok.onError(e -> fail("not an error"));
}
@Test public void error_whenOnError_thenConsume() {
//given
final RuntimeException exception = new RuntimeException();
final Result<Integer> error = Result.error(exception);
final AtomicReference<Throwable> capture = new AtomicReference<>();
//when
error.onError(capture::set);
//then
assertThat(capture).hasValue(exception);
}
@Test
public void success_whenRecover_thenNoChange() {
//given
final Result<Integer> ok = Result.ok(1);
//when
final Result<Integer> recovered = ok.recover(e -> Result.ok(2));
//then
recovered.peek(v -> assertThat(v).isEqualTo(1));
}
@Test
public void error_whenRecover_thenSuccess() {
//given
final Result<Integer> error = Result.error(new RuntimeException());
//when
final Result<Integer> recovered = error.recover(e -> Result.ok(2));
//then
recovered.peek(v -> assertThat(v).isEqualTo(2));
}
@Test
public void error_whenRecoverFails_thenUpdatedError() {
//given
final Result<Integer> error = Result.error(new RuntimeException("original"));
//when
final Result<Integer> recovered = error.recover(e -> Result.error(new RuntimeException("updated")));
//then
recovered.onError(e -> assertThat(e).hasMessage("updated"));
}
@RequiredArgsConstructor @RequiredArgsConstructor
private static class UseCase { private static class UseCase {