apollo-link-schema/README.md

Use a GraphQL Schema to request data

---
title: apollo-link-schema
description: Assists with mocking and server-side rendering
---

The schema link provides a [graphql execution environment](http://graphql.org/graphql-js/graphql/#graphql), which allows you to perform GraphQL operations on a provided schema. This type of behavior is commonly used for server-side rendering (SSR) to avoid network calls and mocking data. While the schema link could provide graphql results on the client, currently the graphql execution layer is [too heavy weight](https://bundlephobia.com/result?p=graphql) for practical application. To unify your state management with client-side GraphQL operations, you should use [apollo-link-state](state), because it integrates with the Apollo Client cache and is much more lightweight.

## Installation

`npm install apollo-link-schema --save`

## Usage

### Server Side Rendering

When performing SSR _on the same server_ you can use this library to avoid making network calls.

```js
import { ApolloClient } from 'apollo-client';
import { InMemoryCache } from 'apollo-cache-inmemory';
import { SchemaLink } from 'apollo-link-schema';

import schema from './path/to/your/schema';

const graphqlClient = new ApolloClient({
  ssrMode: true,
  cache: new InMemoryCache(),
  link: new SchemaLink({ schema })
});
```

### Mocking

For more detailed information about mocking, please look the [graphql-tools documentation](https://www.apollographql.com/docs/graphql-tools/mocking.html).

```js
import { ApolloClient } from 'apollo-client';
import { InMemoryCache } from 'apollo-cache-inmemory';
import { SchemaLink } from 'apollo-link-schema';
import { makeExecutableSchema, addMockFunctionsToSchema } from 'graphql-tools';

const typeDefs = `
  Query {
  ...
  }
`;

const mocks = {
  Query: () => ...,
  Mutation: () => ...
};

const schema = makeExecutableSchema({ typeDefs });
addMockFunctionsToSchema({
  schema,
  mocks
});

const apolloCache = new InMemoryCache(window.__APOLLO_STATE__);

const graphqlClient = new ApolloClient({
  cache: apolloCache,
  link: new SchemaLink({ schema })
});
```

### Options

The `SchemaLink` constructor can be called with an object with the following properties:

* `schema`: an executable graphql schema
* `rootValue`: the root value that is passed to the resolvers (i.e. the first parameter for the [rootQuery](http://graphql.org/learn/execution/#root-fields-resolvers))
* `context`: an object passed to the resolvers, following the [graphql specification](http://graphql.org/learn/execution/#root-fields-resolvers) or a function that accepts the operation and returns the resolver context. The resolver context may contain all the data-fetching connectors for an operation.