mfpiccolo / graphql-normalizr

Normalize GraphQL responses for persisting in the client cache/state

graphql-normalizr

Normalize GraphQL responses for persisting in the client cache/state.

Not related, in any way, to normalizr, just shamelessly piggybacking on it's popularity. Also, "normalizEr" is taken...

TL;DR: Transforms:

{
  "data": {
    "findUser": [
      {
        "__typename": "User",
        "id": "5a6efb94b0e8c36f99fba013",
        "email": "[e-mail]",
        "posts": [
          {
            "__typename": "Post",
            "id": "5a6efb94b0e8c36f99fba016",
            "title": "Dolorem voluptatem molestiae",
            "comments": [
              {
                "__typename": "Comment",
                "id": "5a6efb94b0e8c36f99fba019",
                "message":
                  "Alias quod est voluptatibus aut quis sunt aut numquam."
              },
              {
                "__typename": "Comment",
                "id": "5a6efb94b0e8c36f99fba01b",
                "message": "Harum quia asperiores nemo."
              },
              {
                "__typename": "Comment",
                "id": "5a6efb94b0e8c36f99fba01c",
                "message": "Vel veniam consectetur laborum."
              },
              {
                "__typename": "Comment",
                "id": "5a6efb94b0e8c36f99fba01e",
                "message":
                  "Possimus beatae vero recusandae beatae quas ut commodi laboriosam."
              }
            ]
          }
        ]
      }
    ]
  }
}

into:

{
  "comments": {
    "5a6efb94b0e8c36f99fba019": {
      "id": "5a6efb94b0e8c36f99fba019",
      "message": "Alias quod est voluptatibus aut quis sunt aut numquam."
    },
    "5a6efb94b0e8c36f99fba01b": {
      "id": "5a6efb94b0e8c36f99fba01b",
      "message": "Harum quia asperiores nemo."
    },
    "5a6efb94b0e8c36f99fba01c": {
      "id": "5a6efb94b0e8c36f99fba01c",
      "message": "Vel veniam consectetur laborum."
    },
    "5a6efb94b0e8c36f99fba01e": {
      "id": "5a6efb94b0e8c36f99fba01e",
      "message":
        "Possimus beatae vero recusandae beatae quas ut commodi laboriosam."
    }
  },
  "posts": {
    "5a6efb94b0e8c36f99fba016": {
      "id": "5a6efb94b0e8c36f99fba016",
      "title": "Dolorem voluptatem molestiae",
      "comments": [
        "5a6efb94b0e8c36f99fba019",
        "5a6efb94b0e8c36f99fba01b",
        "5a6efb94b0e8c36f99fba01c",
        "5a6efb94b0e8c36f99fba01e"
      ]
    }
  },
  "users": {
    "5a6efb94b0e8c36f99fba013": {
      "id": "5a6efb94b0e8c36f99fba013",
      "email": "[e-mail]",
      "posts": ["5a6efb94b0e8c36f99fba016"]
    }
  }
}

Motivation

We all love GraphQL and we want to use it. There are tons of libraries and clients out there that help us do that with ease, but there is still one problem... How do you persist that data?

Yes, everything is all great when the response mirrors the exact structure we asked for, but we don't want to cache it that way, do we? We probably want a normalized version of that data which we can persist to our store and read/modify it efficiently. Flux or Redux stores work best with normalized data and there are also GraphQL clients you can use to execute queries on the local cache/state (blips, artemis or apollo-link-state), in which case, we definitely need to persist normalized data.

GraphQLNormalizr is simple, fast, light-weight and it provides all the tools needed to do just that, the only requirement is that you include the id and __typename fields for all the nodes (but it can do that for you if you're too lazy or you want to keep your sources thin).

Table of contents

• Installation
• API by example
  • GraphQLNormalizr
  • parse
  • addRequiredFields
  • normalize

Installation

npm install graphql-normalizr

API by example

The GraphQLNormalizr constructor function returns an object containing 3 methods:

1. parse
2. addRequiredFields
3. normalize

Depending on how you write your queries, you may or may not use parse or addRequiredFields, but normalize is the method that you will transform the GraphQL response. As you've probably seen from the TL;DR, all response nodes must contain the __typename and id fields. __typename is a GraphQL meta field and the id key may be customized when creating the GraphQLNormalizr client.

If your queries already ask for id and __typename there's no need to use parse or addRequiredFields. Otherwise, parse will take care of transforming your GraphQL source into a Document and add the __typename and id fields where needed. In case you already use a different parser, or only have access to the Document you may use addRequiredFields on the Document to add the __typename and id fields

GraphQLNormalizr

import { GraphQLNormalizr } from 'graphql-normalizr'

// const config = ...
const normalizer = new GraphQLNormalizr(config)

config: optional - the configuration object containing information for instantiating the client. it takes the following props:

• idKey
• typeMap
• lists
• typenames
• caching

idKey

String

Default is "id". Configures a custom id key for the client. Use this if your resource identifiers are found under a different key name ('_id', 'key', 'uid' etc).

Consider the following GraphQL response:

const response = {
  data: {
    findUser: {
      __typename: 'User',
      uid: '5a6efb94b0e8c36f99fba013',
      email: '[e-mail]',
    },
  },
}

Normalize the data with our custom id key:

// using destructuring to get the `normalize` method of the client
const { normalize } = new GraphQLNormalizr({ idKey: 'uid' })
normalize(response)
// =>
// {
//  users: {
//    '5a6efb94b0e8c36f99fba013' : {
//      uid: '5a6efb94b0e8c36f99fba013',
//      email: '[e-mail]'
//    }
//  }
// }

typeMap

Object

By default, graphql-normalizr uses pluralize to compute entity names, so a User type will be stored under the users key. Use this to provide different mapping rules between Types and entity names.

const response = {
  data: {
    findUser: {
      __typename: 'User',
      id: '5a6efb94b0e8c36f99fba013',
      email: '[e-mail]',
    },
  },
}

const { normalize } = new GraphQLNormalizr({
  typeMap: { User: 'accounts' },
})
normalize(response)
// =>
// {
//  accounts: {
//    '5a6efb94b0e8c36f99fba013' : {
//      id: '5a6efb94b0e8c36f99fba013',
//      email: '[e-mail]'
//    }
//  }
// }

lists

Boolean

Default is false. All the data is stored in key/value pairs, for easy access. If you want to use arrays, for whatever reason, set this to true

For the same response object in our previous example:

const { normalize } = new GraphQLNormalizr({
  lists: true,
})
normalize(response)
// =>
// {
//  accounts: [
//    {
//      id: '5a6efb94b0e8c36f99fba013',
//      email: '[e-mail]'
//    }
//  ]
// }

typenames

Boolean

Default is false. The normalized data will not contain the __typename field. Set this to true if you need to persist them.

const { normalize } = new GraphQLNormalizr({
  typenames: true,
})

normalize(response)
// =>
// {
//  accounts: {
//    '5a6efb94b0e8c36f99fba013' : {
//      __typename: 'User',
//      id: '5a6efb94b0e8c36f99fba013',
//      email: '[e-mail]'
//    }
//  }
// }

caching

Boolean

Default is false. The normalize method is pretty fast by itself, it does a single iteration and associates the values only for each response node and not for all the fields. Enable this if you think you'd be normalizing the same response multiple times, like when you're polling for data and it may not have changed.

const { normalize } = new GraphQLNormalizr({
  caching: true,
})

const normalized = normalize(response)
const cached = normalize(response)

cached === normalized // => true

parse

Turns a GraphQL source into a Document and adds the required fields where necessary.

// ...
import { GraphQLNormalizr } from 'graphql-normalizr'

const source = `{
  allUsers {
    email
    posts {
      title
      comments {
        message
      }
    }
  }
}`

const { parse } = new GraphQLNormalizr()

const query = parse(source) // will add `id` and `__typename` fields to all the nodes

// We can use the print method from `graphql` to see/use the updated source
const { print } = require('graphql')
print(query)
// =>
// `{
//  allUsers {
//    __typename
//    id
//    email
//    posts {
//      __typename
//      id
//      comments {
//        __typename
//        id
//        message
//      }
//    }
//  }
// }`

// ...

addRequiredFields

If you only have access to the Document, you can use the print method from graphql to get the source and parse it. But that may be expensive and you shouldn't have to print a document just to parse it again. addRequiredFields will add the id and __typename fields to that document, without the need of extracting it's source.

// ...
import { GraphQLNormalizr } from 'graphql-normalizr'
import { allUsersQuery } from './queries'

const { addRequiredFields } = new GraphQLNormalizr()

const query = addRequiredFields(allUsersQuery)

// ...

normalize

The following is a full example where we use apollo-fetch to execute a query and then normalize it with GraphQLNormalizr

const { GraphQLNormalizr } = require('graphql-normalizr')
const { createApolloFetch } = require('apollo-fetch')

const uri = 'http://localhost:8080/graphql'
const fetch = createApolloFetch({ uri })

const source = `
  query {
    allUsers {
      ...userFields
    }
  }
  fragment userFields on User {
    email
    posts {
      title
      comments {
        message
      }
    }
  }
`

const { normalize, parse } = new GraphQLNormalizr()
const query = parse(source)

fetch({ query }).then(response => {
  const normalized = normalize(response)
  // persist the normalized data to our app state.
}).catch(...)