298 lines
No EOL
9.1 KiB
Markdown
298 lines
No EOL
9.1 KiB
Markdown
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<div style="text-align: center">
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<hr>
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<a href="https://pub.dartlang.org/packages/angel_graphql" rel="nofollow"><img src="https://img.shields.io/pub/v/angel_graphql.svg" alt="Pub" data-canonical-src="https://img.shields.io/pub/v/angel_graphql.svg" style="max-width:100%;"></a>
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<a href="https://travis-ci.org/angel-dart/graphql" rel="nofollow"><img src="https://travis-ci.org/angel-dart/graphql.svg" alt="Pub" data-canonical-src="https://img.shields.io/pub/v/angel_graphql.svg" style="max-width:100%;"></a>
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</div>
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* [Installation](#installation)
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* [Usage](#usage)
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* [Subscriptions](#subscriptions)
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* [Integration with Angel `Service`s](#using-services)
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* [Documenting API's](#documentation)
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* [Deprecated - Mirrors Usage](#mirrors)
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A complete implementation of the official
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[GraphQL specification](http://facebook.github.io/graphql/October2016/#sec-Language) - these
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are the [Angel framework](https://angel-dart.github.io)-specific
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bindings.
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The goal of this project is to provide to server-side
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users of Dart an alternative to REST API's. `package:angel_graphql`, which, when combined with the allows
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server-side Dart users to build backends with GraphQL and
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virtually any database imaginable.
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## Installation
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To install `package:angel_graphql`, add the following to your
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`pubspec.yaml`:
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```yaml
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dependencies:
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angel_framework: ^2.0.0-alpha
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angel_graphql: ^1.0.0-alpha
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```
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## Usage
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Using this package is very similar to GraphQL.js - you define
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a schema, and then mount `graphQLHttp` in your router to start
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serving. This implementation supports GraphQL features like
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introspection, so you can play around with `graphiql` as well!
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Firstly, define your schema. A GraphQL schema contains an
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*object type* that defines all querying operations that can be
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applied to the backend.
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A GraphQL schema may also have a *mutation* object type,
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which defines operations that change the backend's state, and
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optionally a *subscription* type, which defines real-time
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interactions (coming soon!).
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You can use the `convertDartType` helper to wrap your existing
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`Model`/PODO classes, and make GraphQL aware of them without duplicated
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effort.
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```dart
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import 'package:angel_framework/angel_framework.dart';
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import 'package:angel_graphql/angel_graphql.dart';
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import 'package:graphql_schema/graphql_schema.dart';
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import 'package:graphql_server/graphql_server.dart';
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import 'package:graphql_server/mirrors.dart';
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Future configureServer(Angel app) async {
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var queryType = objectType(
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'Query',
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description: 'A simple API that manages your to-do list.',
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fields: [
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field(
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'todos',
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listOf(convertDartType(Todo).nonNullable()),
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resolve: resolveViaServiceIndex(todoService),
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),
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field(
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'todo',
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convertDartType(Todo),
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resolve: resolveViaServiceRead(todoService),
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inputs: [
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new GraphQLFieldInput('id', graphQLId.nonNullable()),
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],
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),
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],
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);
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var mutationType = objectType(
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'Mutation',
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description: 'Modify the to-do list.',
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fields: [
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field(
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'create',
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graphQLString,
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),
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],
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);
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var schema = graphQLSchema(
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queryType: queryType,
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mutationType: mutationType,
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);
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}
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```
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After you've created your `GraphQLSchema`, you just need to
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wrap in a call to `graphQLHttp`, a request handler that responds
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to GraphQL.
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In *development*, it's also highly recommended to mount the
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`graphiQL` handler, which serves GraphQL's official visual
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interface, for easy querying and feedback.
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```dart
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app.all('/graphql', graphQLHttp(new GraphQL(schema)));
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app.get('/graphiql', graphiQL());
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```
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All that's left now is just to start the server!
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```dart
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var server = await http.startServer('127.0.0.1', 3000);
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var uri =
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new Uri(scheme: 'http', host: server.address.address, port: server.port);
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var graphiqlUri = uri.replace(path: 'graphiql');
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print('Listening at $uri');
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print('Access graphiql at $graphiqlUri');
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```
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Visit your `/graphiql` endpoint, and you'll see the `graphiql`
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UI, ready-to-go!
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Now you're ready to build a GraphQL API!
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## Subscriptions
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Example:
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https://github.com/angel-dart/graphql/blob/master/angel_graphql/example/subscription.dart
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In GraphQL, as of the June 2018 spec, clients can subscribe to streams of events
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from the server. In your schema, all you need to do is return a `Stream` from a `resolve`
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callback, rather than a plain object:
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```dart
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var postAdded = postService.afterCreated
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.asStream()
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.map((e) => {'postAdded': e.result})
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.asBroadcastStream();
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var schema = graphQLSchema(
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// ...
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subscriptionType: objectType(
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'Subscription',
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fields: [
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field('postAdded', postType, resolve: (_, __) => postAdded),
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],
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),
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);
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```
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By default, `graphQLHttp` has no support for subscriptions, because regular
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HTTP requests are stateless, and are not ideal for continuous data pushing.
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You can add your own handler:
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```dart
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graphQLHttp(graphQL, onSubscription: (req, res, stream) {
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// Do something with the stream here. It's up to you.
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});
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```
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There is, however, `graphQLWS`, which implements Apollo's
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`subscriptions-transport-ws` protocol:
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```dart
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app.get('/subscriptions', graphQLWS(GraphQL(schema)));
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```
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You can then use existing JavaScript clients to handle subscriptions.
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The `graphiQL` handler also supports using subscriptions. In the following snippet, the
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necessary scripts will be added to the rendered page, so that the `subscriptions-transport-ws`
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client can be used by GraphiQL:
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```dart
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app.get('/graphiql',
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graphiQL(subscriptionsEndpoint: 'ws://localhost:3000/subscriptions'));
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```
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**NOTE: Apollo's spec for the aforementioned protocol is very far outdated, and completely inaccurate,**
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**so as of April 18th, 2019, GraphiQL and the `subscriptions-transport-ws` client might not yet work.**
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**See this issue for more:**
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**https://github.com/apollographql/subscriptions-transport-ws/issues/551**
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## Using Services
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What would Angel be without services? For those unfamiliar - in Angel,
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`Service` is a base class that implements CRUD functionality, and serves
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as the database interface within an Angel application. They are well-suited
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for NoSQL or other databases without a schema (they can be used with
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SQL, but that's not their primary focus).
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`package:angel_graphql` has functionality to resolve fields by interacting with
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services.
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Consider our previous example, and note the calls to
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`resolveViaServiceIndex` and `resolveViaServiceRead`:
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```dart
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var queryType = objectType(
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'Query',
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description: 'A simple API that manages your to-do list.',
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fields: [
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field(
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'todos',
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listOf(convertDartType(Todo).nonNullable()),
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resolve: resolveViaServiceIndex(todoService),
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),
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field(
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'todo',
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convertDartType(Todo),
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resolve: resolveViaServiceRead(todoService),
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inputs: [
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new GraphQLFieldInput('id', graphQLId.nonNullable()),
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],
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),
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],
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);
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```
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In all, there are:
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* `resolveViaServiceIndex`
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* `resolveViaServiceFindOne`
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* `resolveViaServiceRead`
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* `resolveViaServiceCreate`
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* `resolveViaServiceModify`
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* `resolveViaServiceUpdate`
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* `resolveViaServiceRemove`
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As one might imagine, using these convenience helpers makes
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it much quicker to implement CRUD functionality in a GraphQL
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API.
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## Documentation
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Using `package:graphql_generator`, you can generate GraphQL schemas for concrete Dart
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types:
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```dart
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configureServer(Angel app) async {
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var schema = graphQLSchema(
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queryType: objectType('Query', fields: [
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field('todos', listOf(todoGraphQLType), resolve: (_, __) => ...)
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]);
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);
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}
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@graphQLClass
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class Todo {
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String text;
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@GraphQLDocumentation(description: 'Whether this item is complete.')
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bool isComplete;
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}
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```
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For more documentation, see:
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https://pub.dartlang.org/packages/graphql_generator
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## Mirrors
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**NOTE: Mirrors support is deprecated, and will not be updated further.**
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The `convertDartType` function can automatically read the documentation
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from a type like the following:
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```dart
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@GraphQLDocumentation(description: 'Any object with a .text (String) property.')
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abstract class HasText {
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String get text;
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}
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@serializable
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@GraphQLDocumentation(
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description: 'A task that might not be completed yet. **Yay! Markdown!**')
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class Todo extends Model implements HasText {
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String text;
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@GraphQLDocumentation(deprecationReason: 'Use `completion_status` instead.')
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bool completed;
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CompletionStatus completionStatus;
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Todo({this.text, this.completed, this.completionStatus});
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}
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@GraphQLDocumentation(description: 'The completion status of a to-do item.')
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enum CompletionStatus { COMPLETE, INCOMPLETE }
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```
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You can also manually provide documentation for
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parameters and endpoints, via a `description` parameter on almost
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all related functions.
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See [`package:graphql_schema`](https://github.com/angel-dart/graphql/tree/master/graphql_schema)
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for more documentation. |