⚠️ NOTICE: This package will be published under rescript-apollo-client going forward

Installation

1. graphql-ppx

We rely on Graphql-ppx for typesafe GraphQL operations and fragments in ReasonML. Go to the official documentation for installation instructions.

You should now have a graphql_schema.json in your project somewhere. Make sure it's always up-to-date!

2. Apollo Client

npm install reason-apollo-client @apollo/client

3. Apollo-Specific graphql-ppx Configuration

Add the following under bs-dependencies and graphql, in your bsconfig.json

{
  "graphql": {
+   "apolloMode": true,
+   "extendMutation": "ApolloClient.GraphQL_PPX.ExtendMutation",
+   "extendQuery": "ApolloClient.GraphQL_PPX.ExtendQuery",
+   "extendSubscription": "ApolloClient.GraphQL_PPX.ExtendSubscription",
+   "templateTagReturnType": "ApolloClient.GraphQL_PPX.templateTagReturnType",
+   "templateTagImport": "gql",
+   "templateTagLocation": "@apollo/client"
  },
  "ppx-flags": ["@reasonml-community/graphql-ppx/ppx"],
  "bs-dependencies: [
    "@reasonml-community/graphql-ppx"
+   "reason-apollo-client"
  ]
}

• "apollo-mode" automaticaly sprinkles __typename throughout our operation and fragment definitions
• "-template-tag-*" is how we tell graphql-ppx to wrap every operation with gql
• "extend-*" allows reason-apollo-client to automatically decorate the generated modules with Apollo-specific things like the correct hook for that operation!

Usage

The EXAMPLES/ directory is the best documentation at the moment (real docs are coming), but in short, the appropriate hook is exposed as a use function on the graphql module. If variables are required, they are the last argument:

module ExampleQuery = [%graphql {|
  query Example ($userId: String!) {
    user(id: $userId) {
      id
      name
    }
  }
|}];

[@react.component]
let make = () => {
  switch (ExampleQuery.use({userId: "1"})) {
    | {data: Some({users})} =>
    ...
  }
}

Other than some slightly different ergonomics, the underlying functionality is almost identical to the official Apollo Client 3 docs, so that is still a good resource for working with this library.

It's probably worth noting this library leverages records heavily which allows for very similar syntax to working with javascript objects and other benefits, but comes with a downside. You may need to annotate the types if you're using a record in a context where the compiler cannot infer what it is. The most common case is when using a non-T-first api like Js.Promise. For this reason we expose every type from the ApolloClient.Types module for convenience. Example:

  let queryResult = SomeQuery.use();

  // I can destructure or access properties just like javascript, and also pattern match!
  switch (queryResult) {
    | {loading: true} =>
      // Show loading
    | {data: Some(data), fetchMore} =>
      let onClick = _ => fetchMore();
      // Show data
  }

  // Annotation is necessary in some cases
  apolloClient.query(~query=(module SomeQuery), ())
  |> Js.Promise.then(result => // Hover over the type and you can see it is an ApolloQueryResult.t__ok
    // Let's open the module so the record fields are accessible
    open ApolloClient.Types.ApolloQueryResult;
    // ☝️ You don't have to go searching for a type, everything is accessible under ApolloClient.Types
    switch (result) {
    | Some(apolloQueryResult) =>
      Js.log2("Got data!", apolloQueryResult.data)
    | Error(_) =>
      Js.log("Check out EXAMPLES/ for T-first promise solutions that don't have this problem!")
    }
  )

Recommended Editor Extensions (Visual Studio Code)

vscode-reasonml-graphql provides syntax highlighting, autocompletion, formatting and more for your graphql operations

vscode-graphiql-explorer provides a visual interface to explore the schema and generate operations

Bindings to JavaScript Packages

Contains partial bindings to the following:

• @apollo/client
• graphql
• subscriptions-transport-ws
• zen-observable

While we strive to provide ergonomics that are intuitive and "reasonable", the intent is to also expose a 1:1 mapping to the javascript package structures if that is your preference. For instance, if you're looking in the Apollo docs and see import { setContext } from '@apollo/link-context' and you'd prefer to interact with this library in the same way, you can always access with the same filepath and name like so:

module Apollo = {
  include ApolloClient.Bindings;
};

// import { setContext } from '@apollo/client/link/context'
let contextLink = Apollo.Client.Link.Context.setContext(...);
// import { createHttpLink } from '@apollo/client'
let httpLink = Apollo.Client.createHttpLink(...);

For comparison, this library packages things up into logical groups that have a consistent structure with the intent to be more disoverable and less reliant on docs:

// Make a generic link
let customLink = ApolloClient.Link.make(...);
// Specific link types are nested under the more general module
let contextLink = ApolloClient.Link.ContextLink.make(...)
// See, they're all the same :)
let httpLink = ApolloClient.Link.HttpLink.make(...)

About This Library

Apollo bindings in the Reason / BuckleScript community are pretty confusing as a write this (July 14, 2020), so it's worth providing some context to help you make the right decisions about which library to use.

This library, reason-apollo-client, targets Apollo Client 3 and aims to take full advantage of v1.0.0 graphql-ppx features and is intended to be a replacement for reason-apollo and reason-apollo-hooks. You should avoid using those libraries at the same time as this one.

If you have a large code base to migrate from reason-apollo-hooks, it might make sense to upgrade to the reason-apollo-hooks PR that adds support for graphql-ppx 1.0 first. This PR has been used by some larger companies to gradually upgrade.

Alternatives

reason-apollo, despite being under the apollographql github org, doesn't have any official Apollo team support behind it and currently seems like it may be abandoned. It binds to the react-apollo js package and some of the older apollo packages not under the @apollo npm namespace.

reason-apollo-hooks is the hooks companion to the reason-apollo library and binds to @apollo/react-hooks. Given the lack of development on reason-apollo, there has been a lot of active contribution pulling reason-apollo features in there. It's fairly battle-tested and it provides a nice, simple interface to hooks. It's not currently compatible with graphql-ppx v1.0.0, but there is a branch that adds basic support for it.

Contributing

Lets work to make the Apollo experience in ReasonML the best experience out there! This is a solid base, but there's a lot of low-hanging fruit remaining—more bindings, docs, examples, tests, better ergonomics—there's so much left to do! Check out the Contributing Guide or issues to get started.