From 248bda0b4f6df9c7eed9b3fd3352ddff80e69e2c Mon Sep 17 00:00:00 2001
From: Paul Campbell <pcampbell@kemitix.net>
Date: Sat, 30 Jun 2018 16:21:07 +0100
Subject: [PATCH] Add `Result.of(Callable)` to reduce boiler plate when calling

---
 .../java/net/kemitix/mon/result/Result.java   | 17 ++++++++++
 src/test/java/net/kemitix/mon/ResultTest.java | 31 +++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/main/java/net/kemitix/mon/result/Result.java b/src/main/java/net/kemitix/mon/result/Result.java
index 70a81e7..30043e2 100644
--- a/src/main/java/net/kemitix/mon/result/Result.java
+++ b/src/main/java/net/kemitix/mon/result/Result.java
@@ -24,6 +24,7 @@ package net.kemitix.mon.result;
 import net.kemitix.mon.Functor;
 import net.kemitix.mon.maybe.Maybe;
 
+import java.util.concurrent.Callable;
 import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
@@ -73,6 +74,22 @@ public interface Result<T> extends Functor<T, Result<?>> {
         return new Success<>(value);
     }
 
+    /**
+     * Create a Result for a output of the Callable.
+     *
+     * @param callable the callable to produce the result
+     * @param <T>      the type of the value
+     * @return a Result
+     */
+    @SuppressWarnings("illegalcatch")
+    static <T> Result<T> of(final Callable<T> callable) {
+        try {
+            return Result.ok(callable.call());
+        } catch (final Exception e) {
+            return Result.error(e);
+        }
+    }
+
     /**
      * Creates a Result from the Maybe, where the Result will be an error if the Maybe is Nothing.
      *
diff --git a/src/test/java/net/kemitix/mon/ResultTest.java b/src/test/java/net/kemitix/mon/ResultTest.java
index 2a2f35e..e8b24cd 100644
--- a/src/test/java/net/kemitix/mon/ResultTest.java
+++ b/src/test/java/net/kemitix/mon/ResultTest.java
@@ -6,6 +6,9 @@ import net.kemitix.mon.result.Result;
 import org.assertj.core.api.WithAssertions;
 import org.junit.Test;
 
+import java.io.IOException;
+import java.util.concurrent.Callable;
+
 public class ResultTest implements WithAssertions {
 
     @Test
@@ -396,6 +399,34 @@ public class ResultTest implements WithAssertions {
         assertThat(toString).contains("Result.Error{error=java.lang.RuntimeException: failed}");
     }
 
+    @Test
+    public void resultOf_okay_isOkay() {
+        //given
+        final Callable<String> c = () -> "okay";
+        //when
+        final Result<String> result = Result.of(c);
+        //then
+        result.match(
+                success -> assertThat(success).isEqualTo("okay"),
+                error -> fail("not an error")
+        );
+    }
+
+    @Test
+    public void resultOf_error_isError() {
+        //given
+        final Callable<String> c = () -> {
+            throw new IOException();
+        };
+        //when
+        final Result<String> result = Result.of(c);
+        //then
+        result.match(
+                success -> fail("not a success"),
+                error -> assertThat(error).isInstanceOf(IOException.class)
+        );
+    }
+
     @RequiredArgsConstructor
     private static class UseCase {