Fastify Typescript: dealing with an unidentified body

I'm new to Fastify and I've encountered a problem with accessing values in the body using Typescript. Does anyone have any ideas or suggestions? Thanks!

Update: I want to simplify my code and avoid using app.get(...)

Here's my code snippet:

App.ts

const buildServer = (options = {}) => {
  const app = fastify(options);
  app.register(routesApiV1, { prefix: '/api'});
  return app;
}

Routes.ts

const routesApiV1: FastifyPluginCallback = (fastify, options, done) => {
  fastify.route(userRoute);
  done();
}

User.ts

const handler: RouteHandlerMethod = async (req, res) => {
  const {
    name,
    lastName,
    dateOfBirth,
    addressLine,
    zipCode,
    city,
    country
  } = req.body; // Property '...' does not exist on type 'unknown'
  
  ...
}

const route: RouteOptions = {
  method: 'GET',
  url: '/user/:id',
  // schema: fastifySchema, Tried but not working
  handler,
  preValidation,
}

Answer №1

The generic type FastifyRequest requires passing your body type as a parameter...

import type { FastifyRequest } from 'fastify'

interface BodyType {
  name: string
}

const handler = async (req: FastifyRequest<{ Body: BodyType }>) => {
    const { name } = req.body
}

When using RouteHandlerMethod, the request object is typed as

FastifyRequest<{ Body: unknown }>
by default, resulting in the body type being unknown.

Answer №2

To ensure proper functionality, it is necessary to define the types for RouteHandlerMethod and RouteOptions as follows:

The types

type Body = {
  name: string;
  // ...
}

type Response = {
   // ...
}

RouteHandlerMethod

import { RawReplyDefaultExpression, RawRequestDefaultExpression, RawServerDefault, RouteHandler, RouteHandlerMethod } from "fastify";

const handler: RouteHandlerMethod<
    RawServerDefault,
    RawRequestDefaultExpression,
    RawReplyDefaultExpression,
    { Reply: Response; Body: Body }
>  = async (req, res) => {
  const {
    name,
    lastName,
    dateOfBirth,
    addressLine,
    zipCode,
    city,
    country
  } = req.body; // Property '...' does not exist on type 'unknown'
  
  ...
}

RouteOptions

import { RawReplyDefaultExpression, RawRequestDefaultExpression, RawServerDefault, RouteHandler, RouteHandlerMethod, RouteOptions } from "fastify";

const route: RouteOptions<RawServerDefault,
RawRequestDefaultExpression,
RawReplyDefaultExpression,
{ Reply: Response, Body: Body }> = {
  method: 'GET',
  url: '/user/:id',
  // schema: fastifySchema, Tried but not working
  handler,
  preValidation,
}

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