Use Relay as React hooks

Install react-relay and relay-hooks using yarn or npm:

yarn add react-relay relay-hooks

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Since queries with useQuery no longer set context, we will expose a new RelayEnvironmentProvider component that takes an environment and sets it in context; variables will no longer be part of context. A RelayEnvironmentProvider should be rendered once at the root of the app, and multiple useQuery's can be rendered under this environment provider.

ReactDOM.render(
    <RelayEnvironmentProvider environment={modernEnvironment}>
      <AppTodo/>
    </RelayEnvironmentProvider>,
    rootElement,
  );

useQuery does not take an environment as an argument. Instead, it reads the environment set in the context; this also implies that it does not set any React context. In addition to query (first argument) and variables (second argument), useQuery accepts a third argument options.

options

fetchPolicy: determine whether it should use data cached in the Relay store and whether to send a network request. The options are:

• store-or-network (default): Reuse data cached in the store; if the whole query is cached, skip the network request
• store-and-network: Reuse data cached in the store; always send a network request.
• network-only: Don't reuse data cached in the store; always send a network request. (This is the default behavior of Relay's existing QueryRenderer.)
• store-only: Reuse data cached in the store; never send a network request.

fetchKey: [Optional] A fetchKey can be passed to force a refetch of the current query and variables when the component re-renders, even if the variables didn't change, or even if the component isn't remounted (similarly to how passing a different key to a React component will cause it to remount). If the fetchKey is different from the one used in the previous render, the current query and variables will be refetched.

networkCacheConfig: [Optional] Object containing cache config options for the network layer. Note the the network layer may contain an additional query response cache which will reuse network responses for identical queries. If you want to bypass this cache completely, pass {force: true} as the value for this option.

import {useQuery, graphql } from 'relay-hooks';

const query = graphql`
  query appQuery($userId: String) {
    user(id: $userId) {
      ...TodoApp_user
    }
  }
`;

const variables = {
  userId: 'me',
}; 

const options = {
  fetchPolicy: 'store-or-network', //default
  networkCacheConfig: undefined,
}

const AppTodo = function (appProps)  {
  const {props, error, retry, cached} = useQuery(query, variables, options);


  if (props && props.user) {
    return <TodoApp user={props.user} />;
  } else if (error) {
    return <div>{error.message}</div>;
  }
  return <div>loading</div>;

}

See useFragment.md

See useRefetch.md

See usePagination.md

See useMutation.md

the useOssFragment is a hooks not provided in the official version of react-relay. Using it you can manage fragment, refetch and pagination containers. For reasons of cost of migration to the react-relay version it is recommended to use the other hooks.

See useOssFragment.md