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* [Installation](#installation)
* [Usage](#usage)
* [Subscriptions](#subscriptions)
* [Integration with Angel `Service`s](#using-services)
* [Documenting API's](#documentation)
* [Deprecated - Mirrors Usage](#mirrors)
A complete implementation of the official
[GraphQL specification](http://facebook.github.io/graphql/October2016/#sec-Language) - these
are the [Angel framework](https://angel-dart.github.io)-specific
bindings.
The goal of this project is to provide to server-side
users of Dart an alternative to REST API's. `package:angel_graphql`, which, when combined with the allows
server-side Dart users to build backends with GraphQL and
virtually any database imaginable.
## Installation
To install `package:angel_graphql`, add the following to your
`pubspec.yaml`:
```yaml
dependencies:
angel_framework: ^2.0.0-alpha
angel_graphql: ^1.0.0-alpha
```
## Usage
Using this package is very similar to GraphQL.js - you define
a schema, and then mount `graphQLHttp` in your router to start
serving. This implementation supports GraphQL features like
introspection, so you can play around with `graphiql` as well!
Firstly, define your schema. A GraphQL schema contains an
*object type* that defines all querying operations that can be
applied to the backend.
A GraphQL schema may also have a *mutation* object type,
which defines operations that change the backend's state, and
optionally a *subscription* type, which defines real-time
interactions (coming soon!).
You can use the `convertDartType` helper to wrap your existing
`Model`/PODO classes, and make GraphQL aware of them without duplicated
effort.
```dart
import 'package:angel_framework/angel_framework.dart';
import 'package:angel_graphql/angel_graphql.dart';
import 'package:graphql_schema/graphql_schema.dart';
import 'package:graphql_server/graphql_server.dart';
import 'package:graphql_server/mirrors.dart';
Future configureServer(Angel app) async {
var queryType = objectType(
'Query',
description: 'A simple API that manages your to-do list.',
fields: [
field(
'todos',
listOf(convertDartType(Todo).nonNullable()),
resolve: resolveViaServiceIndex(todoService),
),
field(
'todo',
convertDartType(Todo),
resolve: resolveViaServiceRead(todoService),
inputs: [
GraphQLFieldInput('id', graphQLId.nonNullable()),
],
),
],
);
var mutationType = objectType(
'Mutation',
description: 'Modify the to-do list.',
fields: [
field(
'create',
graphQLString,
),
],
);
var schema = graphQLSchema(
queryType: queryType,
mutationType: mutationType,
);
}
```
After you've created your `GraphQLSchema`, you just need to
wrap in a call to `graphQLHttp`, a request handler that responds
to GraphQL.
In *development*, it's also highly recommended to mount the
`graphiQL` handler, which serves GraphQL's official visual
interface, for easy querying and feedback.
```dart
app.all('/graphql', graphQLHttp(GraphQL(schema)));
app.get('/graphiql', graphiQL());
```
All that's left now is just to start the server!
```dart
var server = await http.startServer('127.0.0.1', 3000);
var uri =
Uri(scheme: 'http', host: server.address.address, port: server.port);
var graphiqlUri = uri.replace(path: 'graphiql');
print('Listening at $uri');
print('Access graphiql at $graphiqlUri');
```
Visit your `/graphiql` endpoint, and you'll see the `graphiql`
UI, ready-to-go!
Now you're ready to build a GraphQL API!
## Subscriptions
Example:
https://github.com/angel-dart/graphql/blob/master/angel_graphql/example/subscription.dart
In GraphQL, as of the June 2018 spec, clients can subscribe to streams of events
from the server. In your schema, all you need to do is return a `Stream` from a `resolve`
callback, rather than a plain object:
```dart
var postAdded = postService.afterCreated
.asStream()
.map((e) => {'postAdded': e.result})
.asBroadcastStream();
var schema = graphQLSchema(
// ...
subscriptionType: objectType(
'Subscription',
fields: [
field('postAdded', postType, resolve: (_, __) => postAdded),
],
),
);
```
By default, `graphQLHttp` has no support for subscriptions, because regular
HTTP requests are stateless, and are not ideal for continuous data pushing.
You can add your own handler:
```dart
graphQLHttp(graphQL, onSubscription: (req, res, stream) {
// Do something with the stream here. It's up to you.
});
```
There is, however, `graphQLWS`, which implements Apollo's
`subscriptions-transport-ws` protocol:
```dart
app.get('/subscriptions', graphQLWS(GraphQL(schema)));
```
You can then use existing JavaScript clients to handle subscriptions.
The `graphiQL` handler also supports using subscriptions. In the following snippet, the
necessary scripts will be added to the rendered page, so that the `subscriptions-transport-ws`
client can be used by GraphiQL:
```dart
app.get('/graphiql',
graphiQL(subscriptionsEndpoint: 'ws://localhost:3000/subscriptions'));
```
**NOTE: Apollo's spec for the aforementioned protocol is very far outdated, and completely inaccurate,**
**See this issue for more:**
**https://github.com/apollographql/subscriptions-transport-ws/issues/551**
## Using Services
What would Angel be without services? For those unfamiliar - in Angel,
`Service` is a base class that implements CRUD functionality, and serves
as the database interface within an Angel application. They are well-suited
for NoSQL or other databases without a schema (they can be used with
SQL, but that's not their primary focus).
`package:angel_graphql` has functionality to resolve fields by interacting with
services.
Consider our previous example, and note the calls to
`resolveViaServiceIndex` and `resolveViaServiceRead`:
```dart
var queryType = objectType(
'Query',
description: 'A simple API that manages your to-do list.',
fields: [
field(
'todos',
listOf(convertDartType(Todo).nonNullable()),
resolve: resolveViaServiceIndex(todoService),
),
field(
'todo',
convertDartType(Todo),
resolve: resolveViaServiceRead(todoService),
inputs: [
GraphQLFieldInput('id', graphQLId.nonNullable()),
],
),
],
);
```
In all, there are:
* `resolveViaServiceIndex`
* `resolveViaServiceFindOne`
* `resolveViaServiceRead`
* `resolveViaServiceCreate`
* `resolveViaServiceModify`
* `resolveViaServiceUpdate`
* `resolveViaServiceRemove`
As one might imagine, using these convenience helpers makes
it much quicker to implement CRUD functionality in a GraphQL
API.
## Documentation
Using `package:graphql_generator`, you can generate GraphQL schemas for concrete Dart
types:
```dart
configureServer(Angel app) async {
var schema = graphQLSchema(
queryType: objectType('Query', fields: [
field('todos', listOf(todoGraphQLType), resolve: (_, __) => ...)
]);
);
}
@graphQLClass
class Todo {
String text;
@GraphQLDocumentation(description: 'Whether this item is complete.')
bool isComplete;
}
```
For more documentation, see:
https://pub.dartlang.org/packages/graphql_generator
## Mirrors
**NOTE: Mirrors support is deprecated, and will not be updated further.**
The `convertDartType` function can automatically read the documentation
from a type like the following:
```dart
@GraphQLDocumentation(description: 'Any object with a .text (String) property.')
abstract class HasText {
String get text;
}
@serializable
@GraphQLDocumentation(
description: 'A task that might not be completed yet. **Yay! Markdown!**')
class Todo extends Model implements HasText {
String text;
@GraphQLDocumentation(deprecationReason: 'Use `completion_status` instead.')
bool completed;
CompletionStatus completionStatus;
Todo({this.text, this.completed, this.completionStatus});
}
@GraphQLDocumentation(description: 'The completion status of a to-do item.')
enum CompletionStatus { COMPLETE, INCOMPLETE }
```
You can also manually provide documentation for
parameters and endpoints, via a `description` parameter on almost
all related functions.
See [`package:graphql_schema`](https://github.com/angel-dart/graphql/tree/master/graphql_schema)
for more documentation.