Submit.js

import { graphql } from 'react-apollo'
import gql from 'graphql-tag'
import { allPosts, allPostsQueryVars } from './PostList'

function Submit ({ createPost }) {
  function handleSubmit (event) {
    event.preventDefault()

    const form = event.target

    const formData = new window.FormData(form)
    createPost(formData.get('title'), formData.get('url'))

    form.reset()
  }

  return (
    <form onSubmit={handleSubmit}>
      <h1>Apollo: Submit</h1>
      <input placeholder='title' name='title' type='text' required />
      <input placeholder='url' name='url' type='url' required />
      <button type='submit'>Submit</button>
      <style jsx>{`
        form {
          border-bottom: 1px solid #ececec;
          padding-bottom: 20px;
          margin-bottom: 20px;
        }
        h1 {
          font-size: 20px;
        }
        input {
          display: block;
          margin-bottom: 10px;
        }
      `}</style>
    </form>
  )
}

const createPost = gql`
  mutation createPost($title: String!, $url: String!) {
    createPost(title: $title, url: $url) {
      id
      title
      votes
      url
      createdAt
    }
  }
`

export default graphql(createPost, {
  props: ({ mutate }) => ({
    createPost: (title, url) =>
      mutate({
        variables: { title, url },
        update: (proxy, { data: { createPost } }) => {
          const data = proxy.readQuery({
            query: allPosts,
            variables: allPostsQueryVars
          })
          proxy.writeQuery({
            query: allPosts,
            data: {
              ...data,
              allPosts: [createPost, ...data.allPosts]
            },
            variables: allPostsQueryVars
          })
        }
      })
  })
})(Submit)