next.js/examples/with-relay-modern-server-express/lib/withData.js

import React from 'react'
import initEnvironment from './createRelayEnvironment'
import { fetchQuery } from 'react-relay'
import RelayProvider from './RelayProvider'

export default (ComposedComponent, options = {}) => {
  return class WithData extends React.Component {
    static displayName = `WithData(${ComposedComponent.displayName})`

    static async getInitialProps (ctx) {
      // Evaluate the composed component's getInitialProps()
      let composedInitialProps = {}
      if (ComposedComponent.getInitialProps) {
        composedInitialProps = await ComposedComponent.getInitialProps(ctx)
      }

      let queryProps = {}
      let queryRecords = {}
      const environment = initEnvironment()

      if (options.query) {
        const variables = composedInitialProps.relayVariables || {}
        // TODO: Consider RelayQueryResponseCache
        // https://github.com/facebook/relay/issues/1687#issuecomment-302931855
        queryProps = await fetchQuery(environment, options.query, variables)
        queryRecords = environment.getStore().getSource().toJSON()
      }

      return {
        ...composedInitialProps,
        ...queryProps,
        queryRecords
      }
    }

    constructor (props) {
      super(props)
      this.environment = initEnvironment({
        records: props.queryRecords
      })
    }

    render () {
      return (
        <RelayProvider environment={this.environment} variables={{}}>
          <ComposedComponent {...this.props} />
        </RelayProvider>
      )
    }
  }
}