2023-08-16T14:03:22.536Z

src/020-objects/065-common-keys-of-unions-of-objects.problem.ts

@@ -14,6 +14,13 @@ type Organisation = {
   imageId: string;
 };
 
+type Product = {
+  id: string;
+  name: string;
+  price: number;
+  imageId: string;
+};
+
 const getAvatarImage = (entity: unknown) => {
   {
     // Should not be able to access properties that are
@@ -24,6 +31,9 @@ const getAvatarImage = (entity: unknown) => {
 
     // @ts-expect-error
     entity.address;
+
+    // @ts-expect-error
+    entity.price;
   }
 
   return {
@@ -59,3 +69,17 @@ it("Should work for an organisation", () => {
     alt: "Total TypeScript Avatar",
   });
 });
+
+it("Should work for a product", () => {
+  const result = getAvatarImage({
+    id: "1",
+    name: "TypeScript Mug",
+    price: 10,
+    imageId: "abc123",
+  });
+
+  expect(result).toEqual({
+    url: "https://via.placeholder.com/abc123",
+    alt: "TypeScript Mug Avatar",
+  });
+});

src/020-objects/065-common-keys-of-unions-of-objects.solution.ts

@@ -14,7 +14,14 @@ type Organisation = {
   imageId: string;
 };
 
-const getAvatarImage = (entity: User | Organisation) => {
+type Product = {
+  id: string;
+  name: string;
+  price: number;
+  imageId: string;
+};
+
+const getAvatarImage = (entity: User | Organisation | Product) => {
   {
     // Should not be able to access properties that are
     // not common to both types
@@ -24,6 +31,9 @@ const getAvatarImage = (entity: User | Organisation) => {
 
     // @ts-expect-error
     entity.address;
+
+    // @ts-expect-error
+    entity.price;
   }
 
   return {
@@ -59,3 +69,17 @@ it("Should work for an organisation", () => {
     alt: "Total TypeScript Avatar",
   });
 });
+
+it("Should work for a product", () => {
+  const result = getAvatarImage({
+    id: "1",
+    name: "TypeScript Mug",
+    price: 10,
+    imageId: "abc123",
+  });
+
+  expect(result).toEqual({
+    url: "https://via.placeholder.com/abc123",
+    alt: "TypeScript Mug Avatar",
+  });
+});

src/020-objects/068-omit-cant-distribute.explainer.1.ts

@@ -0,0 +1,46 @@
+type User = {
+  id: string;
+  name: string;
+  age: number;
+  imageId: string;
+};
+
+type Organisation = {
+  id: string;
+  name: string;
+  address: string;
+  imageId: string;
+};
+
+type Product = {
+  id: string;
+  name: string;
+  price: number;
+  imageId: string;
+};
+
+type Entity = User | Organisation | Product;
+
+type EntityWithoutId = Omit<Entity, "id">;
+//   ^?
+
+type test = Expect<
+  Equal<
+    EntityWithoutId,
+    | {
+        name: string;
+        age: number;
+        imageId: string;
+      }
+    | {
+        name: string;
+        address: string;
+        imageId: string;
+      }
+    | {
+        name: string;
+        price: number;
+        imageId: string;
+      }
+  >
+>;

src/020-objects/068-omit-cant-distribute.explainer.2.ts

@@ -0,0 +1,50 @@
+type User = {
+  id: string;
+  name: string;
+  age: number;
+  imageId: string;
+};
+
+type Organisation = {
+  id: string;
+  name: string;
+  address: string;
+  imageId: string;
+};
+
+type Product = {
+  id: string;
+  name: string;
+  price: number;
+  imageId: string;
+};
+
+type Entity = User | Organisation | Product;
+
+type DistributiveOmit<T, K extends PropertyKey> = T extends any
+  ? Omit<T, K>
+  : never;
+
+type EntityWithoutId = DistributiveOmit<Entity, "id">;
+//   ^?
+
+type test = Expect<
+  Equal<
+    EntityWithoutId,
+    | {
+        name: string;
+        age: number;
+        imageId: string;
+      }
+    | {
+        name: string;
+        address: string;
+        imageId: string;
+      }
+    | {
+        name: string;
+        price: number;
+        imageId: string;
+      }
+  >
+>;

src/020-objects/069-omit-or-pick-more-than-one-thing.problem.ts

@@ -0,0 +1,29 @@
+interface Product {
+  id: number;
+  name: string;
+  price: number;
+  description: string;
+}
+
+const addProduct = (productInfo: unknown) => {
+  // Do something with the productInfo
+};
+
+addProduct({
+  name: "Book",
+  description: "A book about Dragons",
+});
+
+addProduct({
+  // @ts-expect-error
+  id: 1,
+  name: "Book",
+  description: "A book about Dragons",
+});
+
+addProduct({
+  // @ts-expect-error
+  price: 10,
+  name: "Book",
+  description: "A book about Dragons",
+});

src/020-objects/069-omit-or-pick-more-than-one-thing.solution.1.ts

@@ -0,0 +1,29 @@
+interface Product {
+  id: number;
+  name: string;
+  price: number;
+  description: string;
+}
+
+const addProduct = (productInfo: Omit<Product, "id" | "price">) => {
+  // Do something with the productInfo
+};
+
+addProduct({
+  name: "Book",
+  description: "A book about Dragons",
+});
+
+addProduct({
+  // @ts-expect-error
+  id: 1,
+  name: "Book",
+  description: "A book about Dragons",
+});
+
+addProduct({
+  // @ts-expect-error
+  price: 10,
+  name: "Book",
+  description: "A book about Dragons",
+});

src/020-objects/069-omit-or-pick-more-than-one-thing.solution.2.ts

@@ -0,0 +1,29 @@
+interface Product {
+  id: number;
+  name: string;
+  price: number;
+  description: string;
+}
+
+const addProduct = (productInfo: Pick<Product, "name" | "description">) => {
+  // Do something with the productInfo
+};
+
+addProduct({
+  name: "Book",
+  description: "A book about Dragons",
+});
+
+addProduct({
+  // @ts-expect-error
+  id: 1,
+  name: "Book",
+  description: "A book about Dragons",
+});
+
+addProduct({
+  // @ts-expect-error
+  price: 10,
+  name: "Book",
+  description: "A book about Dragons",
+});