Web Developers : 6-Managing Local State with Apollo by Extending the Client-Side GraphQL Schema

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Managing Local State with Apollo: Extending the Client-Side GraphQL Schema

In modern web development, managing both remote and local state efficiently is crucial for building responsive applications. Apollo Client, a popular state management library for GraphQL, provides powerful tools for managing local state by extending the client-side GraphQL schema. In this blog post, we will explore how to effectively manage local state using Apollo Client and how to extend the GraphQL schema to suit your application’s needs.

What is Apollo Client?

Apollo Client is a comprehensive state management library that allows developers to manage both server-side and client-side data in a seamless manner. It integrates with GraphQL, enabling you to fetch, cache, and manage your data easily. One of the standout features of Apollo Client is its ability to manage local state, which is crucial for building interactive applications.

Understanding Local State Management

Local state refers to the data that is specific to a component or a portion of your application and does not need to be shared across the entire application. This could include UI state, form inputs, or any temporary data that doesn't require persistent storage. Managing local state effectively can improve user experience and performance.

Why Extend the Client-Side GraphQL Schema?

By default, Apollo Client allows you to query remote data from your GraphQL server. However, when it comes to local state, extending the GraphQL schema can help you define your local state management in a structured way. This approach allows you to use GraphQL queries and mutations to manage local state just like you would with remote data.

Step-by-Step Guide to Managing Local State

Step 1: Setting Up Apollo Client

To get started with Apollo Client, you first need to set it up in your React application. Here’s how to do that:

npm install @apollo/client graphql

Next, initialize Apollo Client in your application:

import { ApolloClient, InMemoryCache, ApolloProvider } from '@apollo/client';

const client = new ApolloClient({
  uri: 'https://your-graphql-endpoint.com/graphql',
  cache: new InMemoryCache(), // Enable caching
});

function App() {
  return (
    <ApolloProvider client={client}>
      {/* Your components go here */}
    </ApolloProvider>
  );
}

Step 2: Defining Local State in Your Schema

To manage local state with Apollo Client, you need to extend your GraphQL schema. For instance, if you want to manage a simple toggle state, you can define the following:

import { gql } from '@apollo/client';

const typeDefs = gql`
  extend type Query {
    isToggled: Boolean!
  }

  extend type Mutation {
    toggle: Boolean!
  }
`;

Step 3: Implementing Resolvers for Local State

After defining the schema, you need to implement resolvers that handle the queries and mutations for local state. Here is how you can do it:

const resolvers = {
  Query: {
    isToggled: (_, __, { cache }) => {
      const { isToggled } = cache.readQuery({ query: GET_TOGGLE_STATE });
      return isToggled;
    },
  },
  Mutation: {
    toggle: (_, __, { cache }) => {
      const { isToggled } = cache.readQuery({ query: GET_TOGGLE_STATE });
      const data = { isToggled: !isToggled };
      cache.writeQuery({ query: GET_TOGGLE_STATE, data });
      return data.isToggled;
    },
  },
};

Step 4: Integrating Local State in Your Components

Now, you can integrate your local state management into your components using Apollo’s useQuery and useMutation hooks. Here’s an example:

import { useQuery, useMutation } from '@apollo/client';

const GET_TOGGLE_STATE = gql`
  query GetToggleState {
    isToggled
  }
`;

const TOGGLE_STATE = gql`
  mutation ToggleState {
    toggle
  }
`;

function ToggleComponent() {
  const { data } = useQuery(GET_TOGGLE_STATE);
  const [toggle] = useMutation(TOGGLE_STATE);

  return (
    <div>
      <p>Toggle is {data?.isToggled ? "ON" : "OFF"}</p>
      <button onClick={toggle}>Toggle</button>
    </div>
  );
}

Conclusion

Managing local state in a GraphQL application can be simplified by leveraging Apollo Client’s capabilities to extend the GraphQL schema. By following the steps outlined in this tutorial, you can efficiently manage local state using queries and mutations, making your application more responsive and user-friendly.

As you build more complex applications, remember that Apollo Client provides numerous features to enhance your state management, both locally and remotely. Happy coding!

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