TryLast and variants

scottbilas · Mar 18, 2024 · 7199578 · 7199578
1 parent 531a95c
commit 7199578
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diff --git a/src/Core/EnumerableExtensions.cs b/src/Core/EnumerableExtensions.cs
@@ -81,6 +81,61 @@ public static bool TryFirst<T>(this IEnumerable<T> @this, Func<T, bool> predicat
         return false;
     }
 
+    public static bool TryFirst<T>(this IReadOnlyList<T> @this, out T? found)
+    {
+        if (@this.Count != 0)
+        {
+            found = @this[0];
+            return true;
+        }
+
+        found = default;
+        return false;
+    }
+
+    public static bool TryLast<T>(this IEnumerable<T> @this, out T? found)
+    {
+        var matched = false;
+        found = default;
+
+        foreach (var element in @this)
+        {
+            matched = true;
+            found = element;
+        }
+
+        return matched;
+    }
+
+    public static bool TryLast<T>(this IEnumerable<T> @this, Func<T, bool> predicate, out T? found)
+    {
+        var matched = false;
+        found = default;
+
+        foreach (var element in @this)
+        {
+            if (predicate(element))
+            {
+                matched = true;
+                found = element;
+            }
+        }
+
+        return matched;
+    }
+
+    public static bool TryLast<T>(this IReadOnlyList<T> @this, out T? found)
+    {
+        if (@this.Count != 0)
+        {
+            found = @this[^1];
+            return true;
+        }
+
+        found = default;
+        return false;
+    }
+
     // filtering and searching
 
     public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> @this) where T: class =>

diff --git a/src/Core/EnumerableExtensions.t.cs b/src/Core/EnumerableExtensions.t.cs
@@ -93,6 +93,30 @@ public void TryFirst_WithMatch_ReturnsTrueFound()
         result2.ShouldBe("b");
     }
 
+    [Test]
+    public void TryLast_WithNoMatch_ReturnsFalseDefault()
+    {
+        Array.Empty<string>().TryLast(out var result1).ShouldBeFalse();
+        result1.ShouldBe(default);
+
+        Array.Empty<string>().TryLast(_ => false, out var result2).ShouldBeFalse();
+        result2.ShouldBe(default);
+        new[] { "a", "b" }.TryLast(_ => false, out var result3).ShouldBeFalse();
+        result3.ShouldBe(default);
+    }
+
+    [Test]
+    public void TryLast_WithMatch_ReturnsTrueFound()
+    {
+        var arr = new[] { "b", "a" };
+
+        arr.TryLast(out var result1).ShouldBeTrue();
+        result1.ShouldBe("a");
+
+        arr.TryLast(s => s[0] > 'a', out var result2).ShouldBeTrue();
+        result2.ShouldBe("b");
+    }
+
     [Test]
     public void WhereNotNull_WithItemsWithNulls_ReturnsFilteredForNull()
     {