variant_hpp_typescript_discriminated_union_with_exhaustive_pattern_matching.ts

1import { variant, fields, VariantOf } from 'variant';
2
3// 1. Define your variant structure
4const Message = variant({
5  Chat: fields<{ author: string; body: string }>(),
6  Status: fields<{ online: boolean }>(),
7  Ping: {} // No fields
8});
9
10// 2. Extract the type for use in functions
11type Message = VariantOf<typeof Message>;
12
13// 3. Create instances
14const myMsg = Message.Chat({ author: 'Alice', body: 'Hello World' });
15
16// 4. Use pattern matching
17const output = Message.match(myMsg, {
18  Chat: ({ author, body }) => `${author} says: ${body}`,
19  Status: ({ online }) => `User is ${online ? 'online' : 'offline'}`,
20  Ping: () => 'Pong!'
21});
22
23console.log(output);
24// Output: "Alice says: Hello World"