Merge pull request #36 from kemitix/next

Next

CHANGELOG

@@ -1,6 +1,13 @@
 CHANGELOG
 =========
 
+0.11.0
+
+* Rename `Result.maybeThen()` as `Result.flatMapMaybe()`
+* Add `Maybe.match(Consumer,Runnable)`
+* Add `Maybe.isJust()`
+* Add `Maybe.isNothing()`
+
 0.10.0
 ------
 

src/main/java/net/kemitix/mon/maybe/Just.java

@@ -44,6 +44,16 @@ final class Just<T> implements Maybe<T> {
 
     private final T value;
 
+    @Override
+    public boolean isJust() {
+        return true;
+    }
+
+    @Override
+    public boolean isNothing() {
+        return false;
+    }
+
     @Override
     public <R> Maybe<R> flatMap(final Function<T, Maybe<R>> f) {
         return f.apply(value);
@@ -98,6 +108,11 @@ final class Just<T> implements Maybe<T> {
         // ignore - not nothing
     }
 
+    @Override
+    public void match(final Consumer<T> justMatcher, final Runnable nothingMatcher) {
+        justMatcher.accept(value);
+    }
+
     @Override
     public void orElseThrow(final Supplier<Exception> e) {
         // do not throw

src/main/java/net/kemitix/mon/maybe/Maybe.java

@@ -76,6 +76,20 @@ public interface Maybe<T> extends Functor<T, Maybe<?>> {
         return just(value);
     }
 
+    /**
+     * Checks if the Maybe is a Just.
+     *
+     * @return true if the Maybe is a Just
+     */
+    boolean isJust();
+
+    /**
+     * Checks if the Maybe is Nothing.
+     *
+     * @return true if the Maybe is Nothing
+     */
+    boolean isNothing();
+
     /**
      * Monad binder maps the Maybe into another Maybe using the binder method f.
      *
@@ -149,4 +163,12 @@ public interface Maybe<T> extends Functor<T, Maybe<?>> {
      * @param runnable the runnable to call if this is a Nothing
      */
     void ifNothing(Runnable runnable);
+
+    /**
+     * Matches the Maybe, either just or nothing, and performs either the Consumer, for Just, or Runnable for nothing.
+     *
+     * @param justMatcher    the Consumer to pass the value of a Just to
+     * @param nothingMatcher the Runnable to call if the Maybe is a Nothing
+     */
+    void match(Consumer<T> justMatcher, Runnable nothingMatcher);
 }

src/main/java/net/kemitix/mon/maybe/Nothing.java

@@ -34,10 +34,21 @@ import java.util.stream.Stream;
  * @param <T> the type of the missing content
  * @author Paul Campbell (pcampbell@kemitix.net)
  */
+@SuppressWarnings("methodcount")
 final class Nothing<T> implements Maybe<T> {
 
     static final Maybe<?> INSTANCE = new Nothing<>();
 
+    @Override
+    public boolean isJust() {
+        return false;
+    }
+
+    @Override
+    public boolean isNothing() {
+        return true;
+    }
+
     @Override
     public <R> Maybe<R> flatMap(final Function<T, Maybe<R>> f) {
         return Maybe.nothing();
@@ -79,6 +90,11 @@ final class Nothing<T> implements Maybe<T> {
         runnable.run();
     }
 
+    @Override
+    public void match(final Consumer<T> justMatcher, final Runnable nothingMatcher) {
+        nothingMatcher.run();
+    }
+
     @Override
     public void orElseThrow(final Supplier<Exception> e) throws Exception {
         throw e.get();

src/main/java/net/kemitix/mon/result/Result.java

@@ -129,19 +129,19 @@ public interface Result<T> extends Functor<T, Result<?>> {
      * @param <R>         the type of the updated Result
      * @return a new Maybe within a Result
      */
-    static <T, R> Result<Maybe<R>> maybeThen(Result<Maybe<T>> maybeResult, Function<Maybe<T>, Result<Maybe<R>>> f) {
+    static <T, R> Result<Maybe<R>> flatMapMaybe(Result<Maybe<T>> maybeResult, Function<Maybe<T>, Result<Maybe<R>>> f) {
         return maybeResult.flatMap(f);
     }
 
     /**
-     * Checks of the Result is an error.
+     * Checks if the Result is an error.
      *
      * @return true if the Result is an error.
      */
     boolean isError();
 
     /**
-     * Checks of the Result is a success.
+     * Checks if the Result is a success.
      *
      * @return true if the Result is a success.
      */

src/test/java/net/kemitix/mon/MaybeTest.java

@@ -22,7 +22,7 @@ public class MaybeTest implements WithAssertions {
     @Test
     public void justMustBeNonNull() {
         assertThatNullPointerException().isThrownBy(() -> just(null))
-                                        .withMessageContaining("value");
+                .withMessageContaining("value");
     }
 
     @Test
@@ -84,7 +84,7 @@ public class MaybeTest implements WithAssertions {
     public void toOptional() {
         assertThat(just(1).toOptional()).isEqualTo(Optional.of(1));
         assertThat(nothing()
-                        .toOptional()).isEqualTo(Optional.empty());
+                .toOptional()).isEqualTo(Optional.empty());
     }
 
     @Test
@@ -194,4 +194,69 @@ public class MaybeTest implements WithAssertions {
         assertThat(capture).isTrue();
     }
 
+    @Test
+    public void just_whenMatch_thenJustTriggers() {
+        //given
+        final Maybe<Integer> maybe = Maybe.just(1);
+        //then
+        maybe.match(
+                just -> assertThat(just).isEqualTo(1),
+                () -> fail("Not nothing")
+        );
+    }
+
+    @Test
+    public void nothing_whenMatch_thenNothingTriggers() {
+        //given
+        final Maybe<Integer> maybe = Maybe.nothing();
+        final AtomicBoolean flag = new AtomicBoolean(false);
+        //when
+        maybe.match(
+                just -> fail("Not a just"),
+                () -> flag.set(true)
+        );
+        //then
+        assertThat(flag).isTrue();
+    }
+
+    @Test
+    public void just_isJust_isTrue() {
+        //given
+        final Maybe<Integer> maybe = just(1);
+        //when
+        final boolean isJust = maybe.isJust();
+        //then
+        assertThat(isJust).isTrue();
+    }
+
+    @Test
+    public void just_isNothing_isFalse() {
+        //given
+        final Maybe<Integer> maybe = just(1);
+        //when
+        final boolean isNothing = maybe.isNothing();
+        //then
+        assertThat(isNothing).isFalse();
+    }
+
+    @Test
+    public void nothing_isJust_isFalse() {
+        //given
+        final Maybe<Object> maybe = nothing();
+        //when
+        final boolean isJust = maybe.isJust();
+        //then
+        assertThat(isJust).isFalse();
+    }
+
+    @Test
+    public void nothing_isNothing_isTrue() {
+        //given
+        final Maybe<Object> maybe = nothing();
+        //when
+        final boolean isNothing = maybe.isNothing();
+        //then
+        assertThat(isNothing).isTrue();
+    }
+
 }

src/test/java/net/kemitix/mon/ResultTest.java

@@ -605,24 +605,24 @@ public class ResultTest implements WithAssertions {
     }
 
     @Test
-    public void okayJust_whenMaybeThen_whereOkayJust_thenIsOkayJust() {
+    public void okayJust_whenFlatMapMaybe_whereOkayJust_thenIsOkayJust() {
         //given
         final Result<Maybe<Integer>> okJust = Result.ok(Maybe.just(1));
         //when
-        final Result<Maybe<Integer>> result = Result.maybeThen(okJust, mv -> Result.ok(Maybe.just(2)));
+        final Result<Maybe<String>> result = Result.flatMapMaybe(okJust, maybe -> Result.ok(maybe.flatMap(v -> Maybe.just("2"))));
         //then
         result.match(
-                success -> assertThat(success.toOptional()).contains(2),
+                success -> assertThat(success.toOptional()).contains("2"),
                 error -> fail("Not an error")
         );
     }
 
     @Test
-    public void okayJust_whenMaybeThen_whereOkayNothing_thenIsOkayNothing() {
+    public void okayJust_whenFlatMapMaybe_whereOkayNothing_thenIsOkayNothing() {
         //given
         final Result<Maybe<Integer>> okJust = Result.ok(Maybe.just(1));
         //when
-        final Result<Maybe<Integer>> result = Result.maybeThen(okJust, v -> Result.ok(Maybe.nothing()));
+        final Result<Maybe<String>> result = Result.flatMapMaybe(okJust, maybe -> Result.ok(maybe.flatMap(v -> Maybe.nothing())));
         //then
         result.match(
                 success -> assertThat(success.toOptional()).isEmpty(),
@@ -631,12 +631,12 @@ public class ResultTest implements WithAssertions {
     }
 
     @Test
-    public void okayJust_whenMaybeThen_whereError_thenIsError() {
+    public void okayJust_whenFlatMapMaybe_whereError_thenIsError() {
         //given
         final Result<Maybe<Integer>> okJust = Result.ok(Maybe.just(1));
         final RuntimeException exception = new RuntimeException();
         //when
-        final Result<Maybe<Integer>> result = Result.maybeThen(okJust, v -> Result.error(exception));
+        final Result<Maybe<Integer>> result = Result.flatMapMaybe(okJust, v -> Result.error(exception));
         //then
         result.match(
                 success -> fail("Not a success"),
@@ -645,27 +645,27 @@ public class ResultTest implements WithAssertions {
     }
 
     @Test
-    public void okayNothing_whenMaybeThen_thenDoNotApply() {
+    public void okayNothing_whenFlatMapMaybe_thenDoNotApply() {
         //given
         final Result<Maybe<Integer>> okNothing = Result.ok(Maybe.nothing());
         //when
-        final Result<Maybe<Integer>> result = Result.maybeThen(okNothing, v -> Result.ok(Maybe.just(2)));
+        final Result<Maybe<String>> result = Result.flatMapMaybe(okNothing, maybe -> Result.ok(maybe.flatMap(v -> Maybe.just("2"))));
         //then
-        okNothing.match(
+        result.match(
                 success -> assertThat(success.toOptional()).isEmpty(),
                 error -> fail("Not an error")
         );
     }
 
     @Test
-    public void error_whenMaybeThen_thenDoNotApply() {
+    public void error_whenFlatMapMaybe_thenDoNotApply() {
         //given
         final RuntimeException exception = new RuntimeException();
         final Result<Maybe<Integer>> maybeResult = Result.error(exception);
         //when
-        final Result<Maybe<Integer>> result = Result.maybeThen(maybeResult, v -> Result.ok(Maybe.just(2)));
+        final Result<Maybe<String>> result = Result.flatMapMaybe(maybeResult, maybe -> Result.ok(maybe.flatMap(v -> Maybe.just("2"))));
         //then
-        maybeResult.match(
+        result.match(
                 success -> fail("Not a success"),
                 error -> assertThat(error).isSameAs(exception)
         );