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getContext()

Environment: server.

getContext() enables telefunctions to access contextual information.

// TodoList.telefunc.js
// Environment: server
 
import { getContext } from 'telefunc'
 
export async function onLoad() {
  const context = getContext()
  const { user } = context
  const todoItems = await Todo.findMany({ select: 'text', authorId: user.id })
  return {
    todoItems,
    userName: user.name
  }
}
// TodoList.telefunc.ts
// Environment: server
 
import { getContext } from 'telefunc'
 
export async function onLoad() {
  const context = getContext()
  const { user } = context
  const todoItems = await Todo.findMany({ select: 'text', authorId: user.id })
  return {
    todoItems,
    userName: user.name
  }
}

It's most commonly used for implementing permissions, see Guides > Permissions.

Provide

Before you can use getContext(), you must provide the context object to your Telefunc server middleware, see:

For example:

// server/index.js
// Environment: server
 
// Server entry (Hono)
 
import { Hono } from 'hono'
import { telefunc } from 'telefunc'
 
const app = new Hono()
 
app.all('/_telefunc', async (c) => {
  const httpResponse = await telefunc({
    request: c.req.raw,
    // Provide the context object here:
    context: {
      user: c.get('user')
    }
  })
  return new Response(httpResponse.body, {
    status: httpResponse.statusCode,
    headers: { 'content-type': httpResponse.contentType }
  })
})
 
// Some authentication middleware — sets the user on Hono's context
app.use(async (c, next) => {
  const userId = c.req.cookie('user-id')
  const user = await getUserFromDatabase(userId)
 
  // Or using a third-party authentication provider (e.g. Auth0):
  const user = await authProviderApi.getUser(c.req.headers)
 
  // Authentication middlewares usually provide information
  // about the logged-in user on the context object:
  c.set('user', user)
  await next()
})
// server/index.ts
// Environment: server
 
// Server entry (Hono)
 
import { Hono } from 'hono'
import { telefunc } from 'telefunc'
 
const app = new Hono()
 
app.all('/_telefunc', async (c) => {
  const httpResponse = await telefunc({
    request: c.req.raw,
    // Provide the context object here:
    context: {
      user: c.get('user')
    }
  })
  return new Response(httpResponse.body, {
    status: httpResponse.statusCode,
    headers: { 'content-type': httpResponse.contentType }
  })
})
 
// Some authentication middleware — sets the user on Hono's context
app.use(async (c, next) => {
  const userId = c.req.cookie('user-id')
  const user = await getUserFromDatabase(userId)
 
  // Or using a third-party authentication provider (e.g. Auth0):
  const user = await authProviderApi.getUser(c.req.headers)
 
  // Authentication middlewares usually provide information
  // about the logged-in user on the context object:
  c.set('user', user)
  await next()
})

See also:

Access

If you get this error:

[telefunc][Wrong Usage][getContext()] Cannot access context object, see https://telefunc.com/getContext#access

Then this means that getContext() was called after an await operator:

// TodoList.telefunc.js
 
export async function myTelefunction() {
  await something()
  // ❌ Wrong: getContext() must be called before `await something()`
  const context = getContext()
}
// TodoList.telefunc.ts
 
export async function myTelefunction() {
  await something()
  // ❌ Wrong: getContext() must be called before `await something()`
  const context = getContext()
}

Make sure to call getContext() before any await operators:

// TodoList.telefunc.js
 
export async function myTelefunction() {
  // ✅ Good: getContext() is called before `await`
  const context = getContext()
  await something()
}
// TodoList.telefunc.ts
 
export async function myTelefunction() {
  // ✅ Good: getContext() is called before `await`
  const context = getContext()
  await something()
}

TypeScript

You can use Telefunc.Context to globally set the type of const context = getContext():

// TelefuncContext.d.ts
 
import 'telefunc'
import type { User } from './User.ts'
 
declare module 'telefunc' {
  namespace Telefunc {
    interface Context {
      user: null | User
    }
  }
}
// User.ts
 
export type User = { id: number }
// *.telefunc.ts
 
import { getContext } from 'telefunc'
 
export async function someTelefunction() {
  // TypeScript knows that `user.id` is a `number`
  const { user } = getContext()
}

You can also directly set const context = getContext<MyContext>():

// *.telefunc.ts
 
import { getContext } from 'telefunc'
 
type Context = {
  userId: number
}
 
export async function someTelefunction() {
  // TypeScript knows that `userId` is a `number`
  const { userId } = getContext<Context>()
}

See also