Add Cell<T> utility class

PowerKit.Tests/CellTests.cs

@@ -0,0 +1,99 @@
+using FluentAssertions;
+using PowerKit;
+using Xunit;
+
+namespace PowerKit.Tests;
+
+public class CellTests
+{
+    [Fact]
+    public void TryOpen_Test()
+    {
+        // Arrange
+        var cell = new Cell<int?>();
+        cell.Store(42);
+
+        // Act
+        var result = cell.TryOpen(out var value);
+
+        // Assert
+        result.Should().BeTrue();
+        value.Should().Be(42);
+    }
+
+    [Fact]
+    public void TryOpen_Unset_Test()
+    {
+        // Arrange
+        var cell = new Cell<int?>();
+
+        // Act
+        var result = cell.TryOpen(out var value);
+
+        // Assert
+        result.Should().BeFalse();
+        value.Should().BeNull();
+    }
+
+    [Fact]
+    public void TryOpen_Null_Test()
+    {
+        // Arrange
+        var cell = new Cell<int?>();
+        cell.Store(null);
+
+        // Act
+        var result = cell.TryOpen(out var value);
+
+        // Assert
+        result.Should().BeTrue();
+        value.Should().BeNull();
+    }
+
+    [Fact]
+    public void OpenOrDefault_Test()
+    {
+        // Arrange
+        var cell = new Cell<int?>();
+        cell.Store(42);
+
+        // Act
+        var value = cell.OpenOrDefault();
+        var valueOrFallback = cell.OpenOrDefault(99);
+
+        // Assert
+        value.Should().Be(42);
+        valueOrFallback.Should().Be(42);
+    }
+
+    [Fact]
+    public void OpenOrDefault_Unset_Test()
+    {
+        // Arrange
+        var cell = new Cell<int?>();
+
+        // Act
+        var value = cell.OpenOrDefault();
+        var valueOrFallback = cell.OpenOrDefault(99);
+
+        // Act & assert
+        value.Should().BeNull();
+        valueOrFallback.Should().Be(99);
+    }
+
+    [Fact]
+    public void OpenOrDefault_Null_Test()
+    {
+        // Arrange
+        var cell = new Cell<int?>();
+        cell.Store(null);
+
+        // Act
+        var value = cell.OpenOrDefault();
+        var valueOrFallback = cell.OpenOrDefault(99);
+
+        // Act & assert
+        value.Should().BeNull();
+        valueOrFallback.Should().BeNull();
+    }
+}

PowerKit/Cell.cs

@@ -0,0 +1,42 @@
+namespace PowerKit;
+
+/// <summary>
+/// Container for a value that may or may not be set.
+/// Essentially <see cref="System.Nullable{T}" />, but for cases where null is also a valid value.
+/// </summary>
+internal class Cell<T>
+{
+    private bool _isValueSet;
+    private T _value = default!;
+
+    /// <summary>
+    /// Stores the specified value in the cell.
+    /// </summary>
+    public void Store(T value)
+    {
+        _value = value;
+        _isValueSet = true;
+    }
+
+    /// <summary>
+    /// Tries to retrieve the value stored in the cell.
+    /// Returns <see langword="true" /> if a value has been stored, <see langword="false" /> otherwise.
+    /// </summary>
+    public bool TryOpen(out T value)
+    {
+        if (_isValueSet)
+        {
+            value = _value;
+            return true;
+        }
+
+        value = default!;
+        return false;
+    }
+
+    /// <summary>
+    /// Retrieves the value stored in the cell, or <paramref name="defaultValue" /> if no value has been stored.
+    /// </summary>
+    public T OpenOrDefault(T defaultValue = default!) =>
+        TryOpen(out var value) ? value : defaultValue;
+}