Merge pull request #44 from messerli-informatik-ag/flatten-and-then

Add overload which flattens AndThen

Author: Ruben Schmidmeister

Funcky.Test/OptionTest.cs

@@ -268,6 +268,16 @@ public void GivenAnOptionToAndThenWithAStatementThenItShouldCompile()
             some.AndThen(Statement);
         }
 
+        [Fact]
+        public void GivenAnOptionAndAndAFuncToOptionItShouldBeFlattened()
+        {
+            var none = Option<int>.None();
+            var some = Option.Some(42);
+
+            Assert.False(none.AndThen(value => Option.Some(1337)).Match(false, v => v == 1337));
+            Assert.True(some.AndThen(value => Option.Some(1337)).Match(false, v => v == 1337));
+        }
+
         [Fact]
         public void GivenANoneWithOrElseFuncWeGetTheCorrectValue()
         {

Funcky/Monads/Option.cs

@@ -98,6 +98,12 @@ public Option<TResult> AndThen<TResult>(Func<TItem, TResult> andThenFunction)
                 ? Option.Some(andThenFunction(_item))
                 : Option<TResult>.None();
 
+        public Option<TResult> AndThen<TResult>(Func<TItem, Option<TResult>> andThenFunction)
+            where TResult : notnull
+            => _hasItem
+                ? andThenFunction(_item)
+                : Option<TResult>.None();
+
         public void AndThen(Action<TItem> andThenFunction)
         {
             if (_hasItem)

changelog.md

@@ -12,3 +12,6 @@
 * Add `True` and `False` functions to public API
 * Match of `Result` Monad accepts actions
 * Add `FirstOrNone`, `LastOrNone` and `SingleOrNone` extension functions
+
+## Unreleased
+* Added overload for AndThen which flattens the Option