simple-update.js

import React from 'react';
import { ApolloConsumer } from 'react-apollo';

import Link from './Link';

const FilterLink = ({ filter, children }) => (
  <ApolloConsumer>
    {cache => (
      <Link
        onClick={() => cache.writeData({ data: { modal: { isOpen: true } })}
      >
        {children}
      </Link>
    )}
  </ApolloConsumer>
);

with-read.js

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

import Link from './Link';

const MODAL = gql`{ modal @client { isOpen } }`;

const FilterLink = ({ filter, children }) => (
  <Query query={MODAL}>
    {({ data, client }) => (
      <Link
        onClick={() => client.writeQuery({ query: MODAL, data: { modal: { isOpen: true } })}
      >
        {children}
      </Link>
    )}
  </ApolloConsumer>
);