Add thenWith(Function)

This commit is contained in:
Paul Campbell 2018-07-09 08:00:53 +01:00
parent fb6b65e6de
commit f6eb27450f
6 changed files with 137 additions and 3 deletions

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@ -5,6 +5,7 @@ CHANGELOG
------
* Add `andThen(Function)`
* Add `thenWith(Function)`
0.9.0
-----

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@ -96,6 +96,11 @@ class Err<T> implements Result<T> {
return Result.error(error);
}
@Override
public Result<T> thenWith(final Function<T, WithResultContinuation<T>> f) {
return this;
}
@Override
public boolean equals(final Object other) {
return other instanceof Err && Objects.equals(error, ((Err) other).error);

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@ -202,7 +202,6 @@ public interface Result<T> extends Functor<T, Result<?>> {
*
* <p>Combination of {@link #flatMap(Function)} and {@link #of(Callable)}.</p>
*
* <p>Syntax is:</p>
* <pre><code>
* Integer doSomething() {...}
* String doSomethingElse(final Integer value) {...}
@ -212,9 +211,29 @@ public interface Result<T> extends Functor<T, Result<?>> {
*
* <p>When the Result is an Err, then the original error is carried over and the Callable is never called.</p>
*
* @param f the function to map the Success value to the Callable
* @param f the function to map the Success value into the Callable
* @param <R> the type of the final Result
* @return a new Result
*/
<R> Result<R> andThen(Function<T, Callable<R>> f);
/**
* Perform the continuation with the current Result value then return the current Result, assuming there was no
* error in the continuation.
*
* <pre><code>
* Integer doSomething() {...}
* void doSomethingElse(final Integer value) {...}
* Result&lt;Integer&gt; r = Result.of(() -&gt; doSomething())
* .thenWith(value -&gt; () -&gt; doSomethingElse(value));
* </code></pre>
*
* <p>Where the Result is an Err, then the Result is returned immediately and the continuation is ignored.</p>
* <p>Where the Result is a Success, then if an exception is thrown by the continuation the Result returned will be
* a new error Result containing that exception, otherwise the original Result will be returned.</p>
*
* @param f the function to map the Success value into the result continuation
* @return the Result or a new error Result
*/
Result<T> thenWith(Function<T, WithResultContinuation<T>> f);
}

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@ -100,6 +100,11 @@ class Success<T> implements Result<T> {
return Result.of(f.apply(value));
}
@Override
public Result<T> thenWith(final Function<T, WithResultContinuation<T>> f) {
return f.apply(value).call(this);
}
@Override
public boolean equals(final Object other) {
return other instanceof Success && Objects.equals(value, ((Success) other).value);

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@ -0,0 +1,49 @@
/**
* The MIT License (MIT)
*
* Copyright (c) 2017 Paul Campbell
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies
* or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
* AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package net.kemitix.mon.result;
/**
* A Callable-like interface for performing an action with a Result that, if there are no errors is returned as-is, but
* if there is an error then a new error Result is returned.
*
* @param <T> the type of the current Result value
*/
@FunctionalInterface
public interface WithResultContinuation<T> {
/**
* Method to make use of the Result value.
*
* @throws Exception to replace the current Result with an error
*/
void run() throws Exception;
@SuppressWarnings({"illegalcatch", "javadocmethod"})
default Result<T> call(final Result<T> currentResult) {
try {
run();
} catch (Throwable e) {
return Result.error(e);
}
return currentResult;
}
}

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@ -540,7 +540,7 @@ public class ResultTest implements WithAssertions {
}
@Test
public void error_andThenError_thenError() {
public void error_andThenError_thenOriginalError() {
//given
final RuntimeException exception1 = new RuntimeException();
final Result<Object> error = Result.error(exception1);
@ -553,6 +553,61 @@ public class ResultTest implements WithAssertions {
result.onError(e -> assertThat(e).isSameAs(exception1));
}
@Test
public void success_whenThenWith_whenOkay_thenSuccess() {
//given
final Result<Integer> ok = Result.ok(1);
//when
final Result<Integer> result = ok.thenWith(v -> () -> {
// do something with v
});
//then
assertThat(result.isOkay()).isTrue();
result.peek(v -> assertThat(v).isEqualTo(1));
}
@Test
public void success_whenThenWith_whenError_thenError() {
//given
final Result<Integer> ok = Result.ok(1);
final RuntimeException exception = new RuntimeException();
//when
final Result<Integer> result = ok.thenWith(v -> () -> {
throw exception;
});
//then
assertThat(result.isError()).isTrue();
result.onError(e -> assertThat(e).isSameAs(exception));
}
@Test
public void error_whenThenWith_whenOkay_thenError() {
//given
final RuntimeException exception = new RuntimeException();
final Result<Integer> error = Result.error(exception);
//when
final Result<Integer> result = error.thenWith(v -> () -> {
// do something with v
});
//then
assertThat(result.isError()).isTrue();
result.onError(e -> assertThat(e).isSameAs(exception));
}
@Test
public void error_whenThenWith_whenError_thenOriginalError() {
//given
final RuntimeException exception = new RuntimeException();
final Result<Integer> error = Result.error(exception);
//when
final Result<Integer> result = error.thenWith(v -> () -> {
throw new RuntimeException();
});
//then
assertThat(result.isError()).isTrue();
result.onError(e -> assertThat(e).isSameAs(exception));
}
@RequiredArgsConstructor
private static class UseCase {