@urql/exchange-populate

populate is an exchange for auto-populating fields in your mutations.

Read more about the populateExchange on our docs!

Quick Start Guide

First install @urql/exchange-populate alongside urql:

yarn add @urql/exchange-populate
# or
npm install --save @urql/exchange-populate

You'll then need to add the populateExchange, that this package exposes.

import { createClient, cacheExchange, fetchExchange } from 'urql';
import { populateExchange } from '@urql/exchange-populate';

const client = createClient({
  url: 'http://localhost:1234/graphql',
  exchanges: [populateExchange({ schema }), cacheExchange, fetchExchange],
});

The schema option is the introspection result for your backend graphql schema, more information about how to get your schema can be found in the "Schema Awareness" Page of the Graphcache documentation..

Example usage

Consider the following queries which have been requested in other parts of your application:

# Query 1
{
  todos {
    id
    name
  }
}

# Query 2
{
  todos {
    id
    createdAt
  }
}

Without the populateExchange you may write a mutation like the following which returns a newly created todo item:

# Without populate
mutation addTodo(id: ID!) {
  addTodo(id: $id) {
    id        # To update Query 1 & 2
    name      # To update Query 1
    createdAt # To update Query 2
  }
}

By using populateExchange, you no longer need to manually specify the selection set required to update your other queries. Instead you can just add the @populate directive.

# With populate
mutation addTodo(id: ID!) {
  addTodo(id: $id) @populate
}

Note: The above two mutations produce an identical GraphQL request.