Updated exercises on events definitions and getting state to include …

…union type for events
oskardudycz · Apr 26, 2024 · d83b85b · d83b85b
1 parent 1cfa74b
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diff --git a/...ductionToEventSourcing/02-GettingStateFromEvents/Immutable/GettingStateFromEventsTests.cs b/...ductionToEventSourcing/02-GettingStateFromEvents/Immutable/GettingStateFromEventsTests.cs
@@ -2,32 +2,39 @@
 using Xunit;
 
 namespace IntroductionToEventSourcing.GettingStateFromEvents.Immutable;
+using static ShoppingCartEvent;
 
 // EVENTS
-public record ShoppingCartOpened(
-    Guid ShoppingCartId,
-    Guid ClientId
-);
+public abstract record ShoppingCartEvent
+{
+    public record ShoppingCartOpened(
+        Guid ShoppingCartId,
+        Guid ClientId
+    ): ShoppingCartEvent;
 
-public record ProductItemAddedToShoppingCart(
-    Guid ShoppingCartId,
-    PricedProductItem ProductItem
-);
+    public record ProductItemAddedToShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
 
-public record ProductItemRemovedFromShoppingCart(
-    Guid ShoppingCartId,
-    PricedProductItem ProductItem
-);
+    public record ProductItemRemovedFromShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
 
-public record ShoppingCartConfirmed(
-    Guid ShoppingCartId,
-    DateTime ConfirmedAt
-);
+    public record ShoppingCartConfirmed(
+        Guid ShoppingCartId,
+        DateTime ConfirmedAt
+    ): ShoppingCartEvent;
 
-public record ShoppingCartCanceled(
-    Guid ShoppingCartId,
-    DateTime CanceledAt
-);
+    public record ShoppingCartCanceled(
+        Guid ShoppingCartId,
+        DateTime CanceledAt
+    ): ShoppingCartEvent;
+
+    // This won't allow
+    private ShoppingCartEvent(){}
+}
 
 // VALUE OBJECTS
 public record PricedProductItem(
@@ -55,7 +62,7 @@ public enum ShoppingCartStatus
 
 public class GettingStateFromEventsTests
 {
-    private static ShoppingCart GetShoppingCart(IEnumerable<object> events)
+    private static ShoppingCart GetShoppingCart(IEnumerable<ShoppingCartEvent> events)
     {
         // 1. Add logic here
         throw new NotImplementedException();
@@ -73,7 +80,7 @@ public void GettingState_ForSequenceOfEvents_ShouldSucceed()
         var pairOfShoes = new PricedProductItem(shoesId, 1, 100);
         var tShirt = new PricedProductItem(tShirtId, 1, 50);
 
-        var events = new object[]
+        var events = new ShoppingCartEvent[]
         {
             new ShoppingCartOpened(shoppingCartId, clientId),
             new ProductItemAddedToShoppingCart(shoppingCartId, twoPairsOfShoes),

diff --git a/...roductionToEventSourcing/02-GettingStateFromEvents/Mutable/GettingStateFromEventsTests.cs b/...roductionToEventSourcing/02-GettingStateFromEvents/Mutable/GettingStateFromEventsTests.cs
@@ -2,32 +2,39 @@
 using Xunit;
 
 namespace IntroductionToEventSourcing.GettingStateFromEvents.Mutable;
+using static ShoppingCartEvent;
 
 // EVENTS
-public record ShoppingCartOpened(
-    Guid ShoppingCartId,
-    Guid ClientId
-);
-
-public record ProductItemAddedToShoppingCart(
-    Guid ShoppingCartId,
-    PricedProductItem ProductItem
-);
-
-public record ProductItemRemovedFromShoppingCart(
-    Guid ShoppingCartId,
-    PricedProductItem ProductItem
-);
-
-public record ShoppingCartConfirmed(
-    Guid ShoppingCartId,
-    DateTime ConfirmedAt
-);
-
-public record ShoppingCartCanceled(
-    Guid ShoppingCartId,
-    DateTime CanceledAt
-);
+public abstract record ShoppingCartEvent
+{
+    public record ShoppingCartOpened(
+        Guid ShoppingCartId,
+        Guid ClientId
+    ): ShoppingCartEvent;
+
+    public record ProductItemAddedToShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
+
+    public record ProductItemRemovedFromShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
+
+    public record ShoppingCartConfirmed(
+        Guid ShoppingCartId,
+        DateTime ConfirmedAt
+    ): ShoppingCartEvent;
+
+    public record ShoppingCartCanceled(
+        Guid ShoppingCartId,
+        DateTime CanceledAt
+    ): ShoppingCartEvent;
+
+    // This won't allow
+    private ShoppingCartEvent(){}
+}
 
 // VALUE OBJECTS
 public class PricedProductItem
@@ -60,7 +67,7 @@ public enum ShoppingCartStatus
 
 public class GettingStateFromEventsTests
 {
-    private static ShoppingCart GetShoppingCart(IEnumerable<object> events)
+    private static ShoppingCart GetShoppingCart(IEnumerable<ShoppingCartEvent> events)
     {
         // 1. Add logic here
         throw new NotImplementedException();
@@ -90,7 +97,7 @@ public void GettingState_ForSequenceOfEvents_ShouldSucceed()
                 ProductId = tShirtId, Quantity = 1, UnitPrice = 50
             };
 
-        var events = new object[]
+        var events = new ShoppingCartEvent[]
         {
             new ShoppingCartOpened(shoppingCartId, clientId),
             new ProductItemAddedToShoppingCart(shoppingCartId, twoPairsOfShoes),

diff --git a/Workshops/IntroductionToEventSourcing/Solved/01-EventsDefinition/README.md b/Workshops/IntroductionToEventSourcing/Solved/01-EventsDefinition/README.md
@@ -16,3 +16,6 @@ Create sample events that represent a specific shopping cart. You can do that in
 Events model:
 
 ![events](./assets/events.jpg)
+
+1. Simple events structure [Solution1/EventsDefinitionTests.cs](./Solution1/EventsDefinitionTests.cs).
+2. Events structure with union type to give option to tell that Shopping Cart event is one of the defined types [Solution2/EventsDefinitionTests.cs](./Solution2/EventsDefinitionTests.cs). Read more in [Union types in C#](https://event-driven.io/en/union_types_in_csharp/).
diff --git a/...EventsDefinition/EventsDefinitionTests.cs → ...nition/Solution1/EventsDefinitionTests.cs b/...EventsDefinition/EventsDefinitionTests.cs → ...nition/Solution1/EventsDefinitionTests.cs
@@ -1,7 +1,7 @@
 using FluentAssertions;
 using Xunit;
 
-namespace IntroductionToEventSourcing.EventsDefinition;
+namespace IntroductionToEventSourcing.EventsDefinition.Solution1;
 
 // 1. Define your events and entity here
 

diff --git a/...IntroductionToEventSourcing/Solved/01-EventsDefinition/Solution2/EventsDefinitionTests.cs b/...IntroductionToEventSourcing/Solved/01-EventsDefinition/Solution2/EventsDefinitionTests.cs
@@ -0,0 +1,119 @@
+using FluentAssertions;
+using Xunit;
+
+namespace IntroductionToEventSourcing.EventsDefinition.Solution2;
+using static ShoppingCartEvent;
+
+// 1. Define your events and entity here
+
+// EVENTS
+public abstract record ShoppingCartEvent
+{
+    public record ShoppingCartOpened(
+        Guid ShoppingCartId,
+        Guid ClientId
+    ): ShoppingCartEvent;
+
+    public record ProductItemAddedToShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
+
+    public record ProductItemRemovedFromShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
+
+    public record ShoppingCartConfirmed(
+        Guid ShoppingCartId,
+        DateTime ConfirmedAt
+    ): ShoppingCartEvent;
+
+    public record ShoppingCartCanceled(
+        Guid ShoppingCartId,
+        DateTime CanceledAt
+    ): ShoppingCartEvent;
+
+    // This won't allow
+    private ShoppingCartEvent(){}
+}
+
+// VALUE OBJECTS
+
+public class PricedProductItem
+{
+    public Guid ProductId { get; set; }
+    public decimal UnitPrice { get; set; }
+
+    public int Quantity { get; set; }
+
+    public decimal TotalPrice => Quantity * UnitPrice;
+}
+
+public record ImmutablePricedProductItem(
+    Guid ProductId,
+    int Quantity,
+    decimal UnitPrice
+)
+{
+    public decimal TotalPrice => Quantity * UnitPrice;
+}
+
+// ENTITY
+
+// regular one
+public class ShoppingCart
+{
+    public Guid Id { get; set; }
+    public Guid ClientId { get; set; }
+    public ShoppingCartStatus Status { get; set; }
+    public IList<PricedProductItem> ProductItems { get; set; } = new List<PricedProductItem>();
+    public DateTime? ConfirmedAt { get; set; }
+    public DateTime? CanceledAt { get; set; }
+}
+
+// immutable one
+public record ImmutableShoppingCart(
+    Guid Id,
+    Guid ClientId,
+    ShoppingCartStatus Status,
+    PricedProductItem[] ProductItems,
+    DateTime? ConfirmedAt = null,
+    DateTime? CanceledAt = null
+);
+
+public enum ShoppingCartStatus
+{
+    Pending = 1,
+    Confirmed = 2,
+    Canceled = 4
+}
+
+public class EventsDefinitionTests
+{
+    [Fact]
+    public void AllEventTypes_ShouldBeDefined()
+    {
+        var shoppingCartId = Guid.NewGuid();
+        var clientId = Guid.NewGuid();
+        var pairOfShoes = new PricedProductItem
+        {
+            ProductId = Guid.NewGuid(),
+            Quantity = 1,
+            UnitPrice = 100
+        };
+
+        var events = new object[]
+        {
+            new ShoppingCartOpened(shoppingCartId, clientId),
+            new ProductItemAddedToShoppingCart(shoppingCartId, pairOfShoes),
+            new ProductItemRemovedFromShoppingCart(shoppingCartId, pairOfShoes),
+            new ShoppingCartConfirmed(shoppingCartId, DateTime.UtcNow),
+            new ShoppingCartCanceled(shoppingCartId, DateTime.UtcNow)
+        };
+
+        const int expectedEventTypesCount = 5;
+        events.Should().HaveCount(expectedEventTypesCount);
+        events.GroupBy(e => e.GetType()).Should().HaveCount(expectedEventTypesCount);
+    }
+}
diff --git a/...rcing/Solved/02-GettingStateFromEvents/Immutable/Solution1/GettingStateFromEventsTests.cs b/...rcing/Solved/02-GettingStateFromEvents/Immutable/Solution1/GettingStateFromEventsTests.cs
@@ -2,32 +2,39 @@
 using Xunit;
 
 namespace IntroductionToEventSourcing.GettingStateFromEvents.Immutable.Solution1;
+using static ShoppingCartEvent;
 
 // EVENTS
-public record ShoppingCartOpened(
-    Guid ShoppingCartId,
-    Guid ClientId
-);
-
-public record ProductItemAddedToShoppingCart(
-    Guid ShoppingCartId,
-    PricedProductItem ProductItem
-);
-
-public record ProductItemRemovedFromShoppingCart(
-    Guid ShoppingCartId,
-    PricedProductItem ProductItem
-);
-
-public record ShoppingCartConfirmed(
-    Guid ShoppingCartId,
-    DateTime ConfirmedAt
-);
-
-public record ShoppingCartCanceled(
-    Guid ShoppingCartId,
-    DateTime CanceledAt
-);
+public abstract record ShoppingCartEvent
+{
+    public record ShoppingCartOpened(
+        Guid ShoppingCartId,
+        Guid ClientId
+    ): ShoppingCartEvent;
+
+    public record ProductItemAddedToShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
+
+    public record ProductItemRemovedFromShoppingCart(
+        Guid ShoppingCartId,
+        PricedProductItem ProductItem
+    ): ShoppingCartEvent;
+
+    public record ShoppingCartConfirmed(
+        Guid ShoppingCartId,
+        DateTime ConfirmedAt
+    ): ShoppingCartEvent;
+
+    public record ShoppingCartCanceled(
+        Guid ShoppingCartId,
+        DateTime CanceledAt
+    ): ShoppingCartEvent;
+
+    // This won't allow
+    private ShoppingCartEvent(){}
+}
 
 // VALUE OBJECTS
 public record PricedProductItem(
@@ -60,7 +67,7 @@ public class GettingStateFromEventsTests
     /// </summary>
     /// <param name="events"></param>
     /// <returns></returns>
-    private static ShoppingCart GetShoppingCart(IEnumerable<object> events)
+    private static ShoppingCart GetShoppingCart(IEnumerable<ShoppingCartEvent> events)
     {
         ShoppingCart shoppingCart = null!;
 
@@ -73,7 +80,7 @@ private static ShoppingCart GetShoppingCart(IEnumerable<object> events)
                         opened.ShoppingCartId,
                         opened.ClientId,
                         ShoppingCartStatus.Pending,
-                        Array.Empty<PricedProductItem>()
+                        []
                     );
                     break;
                 case ProductItemAddedToShoppingCart productItemAdded:
@@ -98,11 +105,7 @@ private static ShoppingCart GetShoppingCart(IEnumerable<object> events)
                     {
                         ProductItems = shoppingCart.ProductItems
                             .Select(pi => pi.ProductId == productItemRemoved.ProductItem.ProductId?
-                                new PricedProductItem(
-                                    pi.ProductId,
-                                    pi.Quantity - productItemRemoved.ProductItem.Quantity,
-                                    pi.UnitPrice
-                                )
+                                pi with { Quantity = pi.Quantity - productItemRemoved.ProductItem.Quantity }
                                 :pi
                             )
                             .Where(pi => pi.Quantity > 0)
@@ -140,7 +143,7 @@ public void GettingState_ForSequenceOfEvents_ShouldSucceed()
         var pairOfShoes = new PricedProductItem(shoesId, 1, 100);
         var tShirt = new PricedProductItem(tShirtId, 1, 50);
 
-        var events = new object[]
+        var events = new ShoppingCartEvent[]
         {
             new ShoppingCartOpened(shoppingCartId, clientId),
             new ProductItemAddedToShoppingCart(shoppingCartId, twoPairsOfShoes),