How to define a schema containing a property belonging to a custom type

[leungkinghin-ct]

I am new to typebox and have a question. Currently in our application we defined a schema as following

export const responseSchema = Type.Object({
  resultCode: Type.String(),
  userId: Type.String(),
});

Now we would like to make a change on this schema so it also supports the entire custom type User instead of only userId as following

export type User = { 
   userId: string
   version: number
   createdBy: string
   ... 
   ...
   ...


}

export const responseSchema = Type.Object({
  resultCode: Type.String(),
  user: Type.Object(User), // which introduce compilation error
});

In this case, how can we define the responseSchema by using User directly instead of extracting every properties from User in schema definition?

Thanks

[sinclairzx81]

@leungkinghin-ct Hi,

You can use generic types for this. The following creates a generic ResponseSchema that includes the resultCode and allows for additional properties to be specified by generic parameter.

TypeScript Link Here

import { Type, TProperties, Static } from '@sinclair/typebox'

/** Generic Type To Create Response Structure */
const ResponseSchema = <Properties extends TProperties>(properties: Properties) => Type.Object({ 
  resultCode: Type.String(), 
  ...properties 
})

// A: User
type A = Static<typeof A>
const A = ResponseSchema({
  user: Type.Object({
    userId: Type.String(),
    version: Type.Number(),
    createdBy: Type.String(),
    // ...
  })
})

// B: UserId
type B = Static<typeof B>
const B = ResponseSchema({
  userId: Type.String()
})

Hope this helps
S

[leungkinghin-ct]

@sinclairzx81 Thanks for your example and support.

I am afraid I haven't explained clearly. My main challenge here is to avoid spreading the properties from User type. It is because User type in my project is defined in another lib which is a huge type contains nested object and a lot of properties. I hope it can be reused in my typebox schema but not re-define once again as following approach

export const responseSchema = Type.Object({
  resultCode: Type.String(),
  user: Type.Object({
       userId: Type.String(),
       version: Type.Number(),
       createdBy: Type.String(),
    // ... too many properties and objects below so I am too lazy to redefine again here

   }), 
});

That's why I would like to know if it is possible define a schema with a custom type directly without spreading its all properties. Thanks.

[sinclairzx81]

@leungkinghin-ct Heya,

That's why I would like to know if it is possible define a schema with a custom type directly without spreading its all properties. Thanks.

I'm not sure I follow, but going over your original post, you had the following TypeScript type.. This is defined as follows.

export type User = { 
   userId: string
   version: number
   createdBy: string
   ... 
   ...
   ...
}

Then you suggested that the following raises a compilation error.

export const responseSchema = Type.Object({
  resultCode: Type.String(),
  user: Type.Object(User), // which introduce compilation error
});

Not sure if the User type is a typo, but this error is expected. TypeBox types cannot be constructed from raw TS static types. They need to be constructed as TypeBox types in order to be composed. This is because TypeScript types are erased at compilation. What this means is you will need to replicate the remote library types as TypeBox types in your project.

export const User = Type.Object({
   userId: Type.String(),
   version: Type.Number(),
   createdBy: Type.String()
   ... 
   ...
   ...
})

export const responseSchema = Type.Object({
  resultCode: Type.String(),
  user: User, // no error
});

There tooling available to help you convert TS types to TypeBox types, you can find this at the link below.

TypeBox Workbench Link Here

Alternatively, if you don't care about the schematics, you can just do the following to create a custom type via Unsafe (this isn't recommended, but will let you embed the remote library static type in TypeBox schematics)

type User = { ... }

export const responseSchema = Type.Object({
  resultCode: Type.String(),
  user: Type.Unsafe<User>(Type.Any()) // will give correct inference, but will not validate
});

Does this help?