Schema Inference

Schema Type Inference with Transformations

When using .parseTo() or .custom() methods, your schema may transform input data into a different type. This is where InferIn and InferOut are especially useful.

Example – Mixed Schema with Transformations

import { schema, InferIn, InferOut } from "vkrun";
 
const userSchema = schema().object({
  id: schema().number(),
  name: schema().string(),
  active: schema().boolean().parseTo().string(), // will transform to string
  joinedAt: schema()
    .date()
    .custom<string>((ctx) => {
      ctx.success(ctx.value.toISOString()); // transform to ISO string
    }),
});
 
type UserInput = InferIn<typeof userSchema>;
type UserOutput = InferOut<typeof userSchema>;

Inferred Types

// Input type
type UserInput = {
  id: number;
  name: string;
  active: boolean;
  joinedAt: Date;
};
 
// Output type
type UserOutput = {
  id: number;
  name: string;
  active: string;
  joinedAt: string;
};

This shows how InferOut captures the final transformed shape of the data, while InferIn reflects the original expected input.

Schema OneOf Location