Section 1: Exercise 02: Tree-mendous Mapped Types

01-composing-types/exercise-02/README.md

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+# Exercise 02: Tree-mendous Mapped Types
+
+In this exercise we're going to use one object type to create
+another object type. It's tree-mendously powerful!

01-composing-types/exercise-02/completed/index.ts

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+type Tree = {
+  name: string;
+  height: number;
+  age: number;
+};
+
+type TreeDetails<Type> = {
+  [Key in keyof Type as `get${Capitalize<string & Key>}`]: () => Type[Key];
+};
+
+type OakTree = TreeDetails<Tree>;
+
+const oakData: Tree = {
+  name: "Oak",
+  height: 20,
+  age: 100,
+};
+
+let oak: OakTree = {
+  getName: () => oakData.name,
+  getHeight: () => oakData.height,
+  getAge: () => oakData.age,
+};
+
+console.log(`Name: ${oak.getName()}`);
+console.log(`Height: ${oak.getHeight()}`);
+console.log(`Age: ${oak.getAge()}`);
+
+// ----
+
+type PartialTree<Type> = {
+  [Key in keyof Type]+?: Type[Key];
+};
+
+let partialOak: PartialTree<Tree> = {
+  name: "Oak",
+};
+
+console.log({ partialOak });
+
+// ----
+
+type TreeWithAge<Type extends number> = `Tree with age ${Type}`;
+
+type OldTree = TreeWithAge<ReturnType<OakTree["getAge"]>>;
+
+let oldOak: OldTree = `Tree with age ${oak.getAge()}`;
+
+console.log(oldOak);

01-composing-types/exercise-02/completed/tsconfig.json

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+{
+  "extends": "@total-typescript/tsconfig/tsc/no-dom/app"
+}

01-composing-types/exercise-02/start/index.ts

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+const oakData = {
+  name: "Oak",
+  height: 20,
+  age: 100,
+};
+
+let oak = {
+  getName: () => oakData.name,
+  getHeight: () => oakData.height,
+  getAge: () => oakData.age,
+};
+
+console.log(`Name: ${oak.getName()}`);
+console.log(`Height: ${oak.getHeight()}`);
+console.log(`Age: ${oak.getAge()}`);