Bindings & Variables

In this guide, you will learn how to use bindings and variables in your Pylon project.

pylon.d.ts

The pylon.d.ts file is a TypeScript declaration file that provides type definitions for the Pylon. It is automatically included in your project when you have created your project using npm create pylon@latest. If your project does not have the pylon.d.ts file yey, you can set it up manually by creating a new file in the root of your project and naming it pylon.d.ts.

// pylon.d.ts
import '@getcronit/pylon'
 
declare module '@getcronit/pylon' {
  interface Bindings {}
 
  interface Variables {}
}

You also need to add the pylon.d.ts file to the include array in your tsconfig.json file.

{
  "include": ["pylon.d.ts", "src/**/*.ts"]
}

Note: The Bindings and Variables interfaces are empty by default. You can add your own bindings and variables to them.

Bindings

You can think of bindings as a different term for environment variables that are used in your project. Bindings are used to store sensitive information like API keys, database URLs, etc.

// src/index.ts
import {app, getContext} from '@getcronit/pylon'
 
export const graphql = {
  hello: () => {
    const ctx = getContext()
 
    const secret = ctx.env.SECRET
 
    const authHeader = ctx.req.header('Authorization')
 
    if (authHeader !== secret) {
      return 'You are not authorized'
    }
 
    return 'You are authorized'
  }
}

In the example above, we are using the SECRET binding to authenticate the user. If the Authorization header does not match the SECRET binding, we throw an error.

In the pylon.d.ts file, you can add your bindings like this:

// pylon.d.ts
import '@getcronit/pylon'
 
declare module '@getcronit/pylon' {
  interface Bindings {
    SECRET: string
  }
 
  interface Variables {}
}

Important: Make sure to add the SECRET binding to your environment. This can differ depeding on your runtime environment. Most of the time, you can add the binding to your .env file.

SECRET=your-secret

Variables

Variables are used to store date inside the request context. Set variables are then available everywhere during the request lifecycle.

// src/index.ts
 
import {app, getContext} from '@getcronit/pylon'
 
export const graphql = {
  hello: () => {
    const ctx = getContext()
 
    const user = ctx.get('user')
 
    if (!user) {
      return 'Hello Stranger'
    }
 
    return `Hello ${user}`
  }
}
 
app.use(async (ctx, next) => {
  // This middleware is executed before the `hello` resolver
 
  const authHeader = ctx.req.header('Authorization')
  const secret = ctx.env.SECRET
 
  if (authHeader === secret) {
    ctx.set('user', 'John Doe')
  }
 
  await next()
})

In the example above, we are setting the user variable in the request context. The user variable is then available in the hello resolver.

In the pylon.d.ts file, you can add your variables like this:

// pylon.d.ts
import '@getcronit/pylon'
 
declare module '@getcronit/pylon' {
  interface Bindings {
    SECRET: string
  }
 
  interface Variables {
    user?: string
  }
}