2023-09-19T11:01:48.172Z

src/075-designing-your-types/177-domain-modelling-in-typescript.explainer.ts

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+// Modelling your domain in TypeScript
+
+// Think of the entities in your domain as individual types
+
+// Compose those types together
+
+// Think about types as containers for other types

src/075-designing-your-types/179-multiple-type-parameters.problem.ts

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+type PromiseFunc = (input: any) => Promise<any>;
+
+type Example1 = PromiseFunc<string, string>;
+
+type test1 = Expect<Equal<Example1, (input: string) => Promise<string>>>;
+
+type Example2 = PromiseFunc<boolean, number>;
+
+type test2 = Expect<Equal<Example2, (input: boolean) => Promise<number>>>;

src/075-designing-your-types/179-multiple-type-parameters.solution.ts

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+type PromiseFunc<Input, Output> = (input: Input) => Promise<Output>;
+
+type Example1 = PromiseFunc<string, string>;
+
+type test1 = Expect<Equal<Example1, (input: string) => Promise<string>>>;
+
+type Example2 = PromiseFunc<boolean, number>;
+
+type test2 = Expect<Equal<Example2, (input: boolean) => Promise<number>>>;

src/075-designing-your-types/182-type-helper-constraints.problem.ts

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+type Result<TResult, TError = Error> =
+  | {
+      success: true;
+      data: TResult;
+    }
+  | {
+      success: false;
+      error: TError;
+    };
+
+type BadExample = Result<
+  { id: string },
+  // @ts-expect-error Should be an object with a message property
+  string
+>;
+
+type GoodExample = Result<{ id: string }, TypeError>;
+type GoodExample2 = Result<{ id: string }, { message: string; code: number }>;
+type GoodExample3 = Result<{ id: string }, { message: string }>;
+type GoodExample4 = Result<{ id: string }>;

src/075-designing-your-types/182-type-helper-constraints.solution.ts

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+type Result<TResult, TError extends { message: string } = Error> =
+  | {
+      success: true;
+      data: TResult;
+    }
+  | {
+      success: false;
+      error: TError;
+    };
+
+type BadExample = Result<
+  { id: string },
+  // @ts-expect-error Should be an object with a message property
+  string
+>;
+
+type GoodExample = Result<{ id: string }, TypeError>;
+type GoodExample2 = Result<{ id: string }, { message: string; code: number }>;
+type GoodExample3 = Result<{ id: string }, { message: string }>;
+type GoodExample4 = Result<{ id: string }>;

src/075-designing-your-types/183-tighter-version-of-omit.problem.ts

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+type StrictOmit<T, K> = Omit<T, K>;
+
+type ShouldFail = StrictOmit<
+  { a: string },
+  // @ts-expect-error
+  "b"
+>;
+
+type tests = [
+  Expect<Equal<StrictOmit<{ a: string; b: number }, "b">, { a: string }>>,
+  Expect<Equal<StrictOmit<{ a: string; b: number }, "b" | "a">, {}>>,
+  Expect<
+    Equal<StrictOmit<{ a: string; b: number }, never>, { a: string; b: number }>
+  >,
+];

src/075-designing-your-types/183-tighter-version-of-omit.solution.ts

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+type StrictOmit<T, K extends keyof T> = Omit<T, K>;
+
+type ShouldFail = StrictOmit<
+  { a: string },
+  // @ts-expect-error
+  "b"
+>;
+
+type tests = [
+  Expect<Equal<StrictOmit<{ a: string; b: number }, "b">, { a: string }>>,
+  Expect<Equal<StrictOmit<{ a: string; b: number }, "b" | "a">, {}>>,
+  Expect<
+    Equal<StrictOmit<{ a: string; b: number }, never>, { a: string; b: number }>
+  >,
+];