Rapid achieves full-stack type-safety via a common technique called "code generation". Whenever the Rapid server starts or when the rapid build command is run, the compiler will parse every route handler inside of your project and generate a bindings.ts file like the below:

// @generated automatically by Rapid-web (https://rapidframework.dev). DO NOT CHANGE OR EDIT THIS FILE!

export interface Handlers {
	queries: {
		"index": {
  			output: any
  			type: 'query'
  			isDynamic: false
		},
	},
	mutations: {},
}

export const routes = {
	"index": {
		url: '/',
		type: 'query',
	},
} as const

This generated file is then consumed on the frontend by Rapid's request client called Bolt. For more info, see the client-side doc here

Special types

Rapid exports special types that enable you to specify complex typescript types for your frontend right inside of your rust route handlers.

Union

A small rust struct that is used by the Rapid compiler to a specify a normal union type in typescript (like type Union = string | number) as the output type for a given handler.

use rapid_web::actix::HttpResponse;
use rapid_web::{rapid_web_codegen::rapid_handler, types::Union};

// Use the "Union" type to handle cases where a route handler might return 2 possible output types (like a success or error value)
pub type RapidOutput = Union<String, Error>;


//...