Zod•2y ago

k9 - Hello! I'm getting up to speed. The Comple...

Hello! I'm getting up to speed. The Complex Schema Validation section of zod-tutorial talks about how to preresent what would be a union type in a schema. That doesn't quite do what I'm looking for

I have defined types with a string template type e.g.

export type PlayerId = `p${string}`;
export type GameId = `g${string}`;
export type SpectatorId = `s${string}`;

export type PlayerId = `p${string}`;
export type GameId = `g${string}`;
export type SpectatorId = `s${string}`;

which has been a useful way to ensure we don't send the wrong IDs throughout our ecosystem. Those IDs come through JSON schemas I would like to validate with Zod.

I can represent validations (there's already methods that ensure the strings are of their type, e.g.

export function isGameId(object: any): object is GameId {
  return object?.charAt?.(0) === 'g';
}

export function isGameId(object: any): object is GameId {
  return object?.charAt?.(0) === 'g';
}

So, erm, so GameId is everywhere in the codebase, so I have to be careful about refactoring the API. But how can I define a type that a) only accepts a string and b) only if it matches type GameId and c) z.infer() can describe it as type

GameId

GameId

Solution

Should just be the following:

type GameId = `g${string}`;

const isGameId = (value: unknown): value is GameId => {
  return typeof value === "string" && value.startsWith("g");
};

const schema = z.string().refine(isGameId);
const result = schema.parse("g123");
//    ^? `g${string}`

type GameId = `g${string}`;

const isGameId = (value: unknown): value is GameId => {
  return typeof value === "string" && value.startsWith("g");
};

const schema = z.string().refine(isGameId);
const result = schema.parse("g123");
//    ^? `g${string}`

Jump to solution

Solution

Sikari•3/26/24, 3:27 AM

Should just be the following:

type GameId = `g${string}`;

const isGameId = (value: unknown): value is GameId => {
  return typeof value === "string" && value.startsWith("g");
};

const schema = z.string().refine(isGameId);
const result = schema.parse("g123");
//    ^? `g${string}`

type GameId = `g${string}`;

const isGameId = (value: unknown): value is GameId => {
  return typeof value === "string" && value.startsWith("g");
};

const schema = z.string().refine(isGameId);
const result = schema.parse("g123");
//    ^? `g${string}`

Sikari•3/26/24, 3:29 AM

Depending on if you consider just valid, you might want to also have a min length on the string, something along the lines of: to make sure you have a string that has and at least one character after.

Sikari•3/26/24, 3:31 AM

And if your

is

is

function is just for Zod, you can get rid of the string check as well.

Scott Trinh•3/26/24, 3:33 AM

There is also which is mentioned in the docs for precisely this use case: https://zod.dev/?id=custom-schemas

GitHub

TypeScript-first schema validation with static type inference

Scott Trinh•3/26/24, 3:35 AM

https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAbzgLzgXzgMyhEcBEyEAJvgNwBQFMAnmAKZwDiAhiPQJLFwC8cABgHMAJAgDOMKMAB2gtP0oUAxhGkS4wMa3ZdecABQA3FgBsArvQBccM9IDW0iAHdpASmvHzjTczaduPAB8iBRwcFD0MGZQ0nC0DBCYcJ4WvDx8+BJSsvhwAGR5yaYWAHQSLLBiAOrAMAAW+viC+K6UaIoqavDa-nrIJUpmErgAPD1cgfqa48StyqrqEWJmJvB8MyVgFWL0jYIAjABMAMwtlAD052FhAHoA-EA

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k9OP•3/26/24, 10:35 AM

Fantastic, wow, thank you!