Using Apollo with TypeScript

Note: Apollo no longer ships with Flow types. If you want to help contribute to add these, please reach out!

As your application grows, you may find it helpful to include a type system to assist in development. Apollo supports type definitions for TypeScript out of the box. Both apollo-client and react-apollo ship with definitions in their npm packages, so installation should be done for you after the libraries are included in your project.

These docs assume you already have TypeScript configured in your project, if not start here.

The most common need when using type systems with GraphQL is to type the results of an operation. Given that a GraphQL server’s schema is strongly typed, we can even generate TypeScript definitions automatically using a tool like apollo-codegen. In these docs however, we will be writing result types manually.

Typing the Component APIs

Using Apollo together with TypeScript couldn’t be easier than using it with component API released in React Apollo 2.1:

interface Data {
  allPeople: {
    people: Array<{ name: string }>;
  };
};

interface Variables {
  first: number;
};

class AllPeopleQuery extends Query<Data, Variables> {}

Now we can use AllPeopleQuery in place of Query in our tree to get full TypeScript support! Since we are not mapping any props coming into our component, nor are we rewriting the props passed down, we only need to provide the shape of our data and the variables required for it to work! Everything else is handled by React Apollo’s robust type definitions.

This approach is the exact same for the <Query />, <Mutation />, and <Subcription /> components! Learn it once, and get the best types ever with Apollo.

Typing the Higher Order Components

Since the result of a query will be sent to the wrapped component as props, we want to be able to tell our type system the shape of those props. Here is an example setting types for an operation using the graphql higher order component (note: the follow sections also work for the query, mutation, and subscription hocs):

import React from "react";
import gql from "graphql-tag";
import { graphql } from "react-apollo";

const HERO_QUERY = gql`
  query GetCharacter($episode: Episode!) {
    hero(episode: $episode) {
      name
      id
      friends {
        name
        id
        appearsIn
      }
    }
  }
`;

type Hero = {
  name: string;
  id: string;
  appearsIn: string[];
  friends: Hero[];
};

type Response = {
  hero: Hero;
};

type Variables = {
  episode: string;
};

// Note that the first parameter here is an empty Object, which means we're
// not checking incoming props for type safety in this example. The next
// example (in the "Options" section) shows how the type safety of incoming
// props can be ensured.
const withCharacter = graphql<{}, Response, Variables>(HERO_QUERY, {
  options: () => ({
    variables: { episode: "JEDI" }
  })
});

export default withCharacter(({ data: { loading, hero, error } }) => {
  if (loading) return <div>Loading</div>;
  if (error) return <h1>ERROR</h1>;
  return ...// actual component with data;
});

Options

Typically, variables to the query will be computed from the props of the wrapper component. Wherever the component is used in your application, the caller would pass arguments that we want our type system to validate what the shape of these props could look like. Here is an example setting the type of props:

import React from "react";
import gql from "graphql-tag";
import { graphql } from "react-apollo";

const HERO_QUERY = gql`
  query GetCharacter($episode: Episode!) {
    hero(episode: $episode) {
      name
      id
      friends {
        name
        id
        appearsIn
      }
    }
  }
`;

type Hero = {
  name: string;
  id: string;
  appearsIn: string[];
  friends: Hero[];
};

type Response = {
  hero: Hero;
};

type InputProps = {
  episode: string;
};

type Variables = {
  episode: string;
};

const withCharacter = graphql<InputProps, Response, Variables>(HERO_QUERY, {
  options: ({ episode }) => ({
    variables: { episode }
  }),
});

export default withCharacter(({ data: { loading, hero, error } }) => {
  if (loading) return <div>Loading</div>;
  if (error) return <h1>ERROR</h1>;
  return ...// actual component with data;
});

This is especially helpful when accessing deeply nested objects that are passed down to the component through props. For example, when adding prop types, a project using TypeScript will begin to surface errors where props being passed are invalid:

import React from "react";
import { ApolloClient } from "apollo-client";
import { createHttpLink } from "apollo-link-http";
import { InMemoryCache } from "apollo-cache-inmemory";
import { ApolloProvider } from "react-apollo";

import Character from "./Character";

export const link = createHttpLink({
  uri: "https://mpjk0plp9.lp.gql.zone/graphql"
});

export const client = new ApolloClient({
  cache: new InMemoryCache(),
  link,
});

export default () =>
  <ApolloProvider client={client}>
    // $ExpectError property `episode`. Property not found in. See: src/Character.js:43
    <Character />
  </ApolloProvider>;

Props

One of the most powerful feature of the React integration is the props function which allows you to reshape the result data from an operation into a new shape of props for the wrapped component. GraphQL is awesome at allowing you to only request the data you want from the server. The client still often needs to reshape or do client side calculations based on these results. The return value can even differ depending on the state of the operation (i.e loading, error, recieved data), so informing our type system of choice of these possible values is really important to make sure our components won’t have runtime errors.

The graphql wrapper from react-apollo supports manually declaring the shape of your result props.

import React from "react";
import gql from "graphql-tag";
import { graphql, ChildDataProps } from "react-apollo";

const HERO_QUERY = gql`
  query GetCharacter($episode: Episode!) {
    hero(episode: $episode) {
      name
      id
      friends {
        name
        id
        appearsIn
      }
    }
  }
`;

type Hero = {
  name: string;
  id: string;
  appearsIn: string[];
  friends: Hero[];
};

type Response = {
  hero: Hero;
};

type InputProps = {
  episode: string
};

type Variables = {
  episode: string
};

type ChildProps = ChildDataProps<InputProps, Response, Variables>;

const withCharacter = graphql<InputProps, Response, Variables, ChildProps>(HERO_QUERY, {
  options: ({ episode }) => ({
    variables: { episode }
  }),
  props: ({ data }) => ({ ...data })
});

export default withCharacter(({ loading, hero, error }) => {
  if (loading) return <div>Loading</div>;
  if (error) return <h1>ERROR</h1>;
  return ...// actual component with data;
});

Since we have typed the response shape, the props shape, and the shape of what will be passed to the client, we can prevent errors in multiple places. Our options and props function within the graphql wrapper are now type safe, our rendered component is protected, and our tree of components have their required props enforced.

export const withCharacter = graphql<InputProps, Response, Variables, Props>(HERO_QUERY, {
  options: ({ episode }) => ({
    variables: { episode }
  }),
  props: ({ data, ownProps }) => ({
    ...data,
    // $ExpectError [string] This type cannot be compared to number
    episode: ownProps.episode > 1,
    // $ExpectError property `isHero`. Property not found on object type
    isHero: data && data.hero && data.hero.isHero
  })
});

With this addition, the entirety of the integration between Apollo and React can be statically typed. When combined with the strong tooling each system provides, it can make for a much improved application and developer experience.

Classes vs Functions

All of the above examples show wrapping a component which is just a function using the result of a graphql wrapper. Sometimes, components that depend on GraphQL data require state and are formed using the class MyComponent extends React.Component practice. In these use cases, TypeScript requires adding prop shape to the class instance. In order to support this, react-apollo exports types to support creating result types easily.

import { ChildProps } from "react-apollo";

const withCharacter = graphql<InputProps, Response>(HERO_QUERY, {
  options: ({ episode }) => ({
    variables: { episode }
  })
});

class Character extends React.Component<ChildProps<InputProps, Response>, {}> {
  render(){
    const { loading, hero, error } = this.props.data;
    if (loading) return <div>Loading</div>;
    if (error) return <h1>ERROR</h1>;
    return ...// actual component with data;
  }
}

export default withCharacter(Character);

Using the name property

If you are using the name property in the configuration of the graphql wrapper, you will need to manually attach the type of the response to the props function. An example using TypeScript would be like this:

import { NamedProps, QueryProps } from 'react-apollo';

export const withCharacter = graphql<InputProps, Response, {}, Prop>(HERO_QUERY, {
  name: 'character',
  props: ({ character, ownProps }: NamedProps<{ character: QueryProps & Response }, Props) => ({
    ...character,
    // $ExpectError [string] This type cannot be compared to number
    episode: ownProps.episode > 1,
    // $ExpectError property `isHero`. Property not found on object type
    isHero: character && character.hero && character.hero.isHero
  })
});
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