Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/ziprandom/graphql-crystal

a graphql implementation for crystal
https://github.com/ziprandom/graphql-crystal

Last synced: about 1 month ago
JSON representation

a graphql implementation for crystal

Awesome Lists containing this project

README 

        
# graphql-crystal [![Build Status](https://api.travis-ci.org/ziprandom/graphql-crystal.svg)](https://travis-ci.org/ziprandom/graphql-crystal)



An implementation of [GraphQL](http://graphql.org/learn/) for the crystal programming language inspired by [graphql-ruby](https://github.com/rmosolgo/graphql-ruby) & [go-graphql](https://github.com/playlyfe/go-graphql) & [graphql-parser](https://github.com/graphql-dotnet/parser).



The library is in beta state atm. Should already be usable but expect to find bugs (and open issues about them). pull-requests, suggestions & criticism are very welcome!



Find the api docs [here](https://ziprandom.github.io/graphql-crystal/).



## Installation



Add this to your application's `shard.yml`:



```yaml

dependencies:

  graphql-crystal:

    github: ziprandom/graphql-crystal

```



## Usage



Complete source [here](example/simple_example.cr).



Given this simple domain model of users and posts



```cr

class User

  property name

  def initialize(@name : String); end

end



class Post

  property :title, :body, :author

  def initialize(@title : String, @body : String, @author : User); end

end



POSTS = [] of Post

USERS = [User.new("Alice"), User.new("Bob")]

```



We can instantiate a GraphQL schema directly from a graphql schema definition string



```cr

schema = GraphQL::Schema.from_schema(

  %{

    schema {

      query: QueryType,

      mutation: MutationType

    }



    type QueryType {

      posts: [PostType]

      users: [UserType]

      user(name: String!): UserType

    }



    type MutationType {

      post(post: PostInput) : PostType

    }



    input PostInput {

      author: String!

      title: String!

      body: String!

    }



    type UserType {

      name: String

      posts: [PostType]

    }



    type PostType {

      author: UserType

      title: String

      body: String

    }

  }

)

```



Then we create the backing types by including the ```GraphQL::ObjectType``` and defining the fields using the ```field``` macro



```cr

# reopening User and Post class

class User

  include GraphQL::ObjectType



  # defaults to the method of

  # the same name without block

  field :name



  field :posts do

    POSTS.select &.author.==(self)

  end

end



class Post

  include GraphQL::ObjectType

  field :title

  field :body

  field :author

end

```



Now we define the top level queries



```cr

# extend self when using a module or a class (not an instance)

# as the actual Object



module QueryType

  include GraphQL::ObjectType

  extend self



  field :users do

    USERS

  end



  field :user do |args|

    USERS.find( &.name.==(args["name"].as(String)) ) || raise "no user by that name"

  end



  field :posts do

    POSTS

  end

end



module MutationType

  include GraphQL::ObjectType

  extend self



  field :post do |args|



    user = USERS.find &.name.==(

      args["post"].as(Hash)["author"].as(String)

    )

    raise "author doesn't exist" unless user



    (

      POSTS << Post.new(

        args["post"].as(Hash)["title"].as(String),

        args["post"].as(Hash)["body"].as(String),

        user

      )

    ).last

  end

end

```



Finally set the top level Object Types on the schema



```cr

schema.query_resolver = QueryType

schema.mutation_resolver = MutationType

```



And we are ready to run some tests



```cr

describe "my graphql schema" do

  it "does queries" do

    schema.execute("{ users { name posts } }")

      .should eq ({

                    "data" => {

                      "users" => [

                        {

                          "name" => "Alice",

                          "posts" => [] of String

                        },

                        {

                          "name" => "Bob",

                          "posts" => [] of String

                        }

                      ]

                    }

                  })

  end



  it "does mutations" do



    mutation_string = %{

      mutation post($post: PostInput) {

        post(post: $post) {

          author {

            name

            posts { title }

          }

          title

          body

        }

      }

    }



    payload = {

      "post" => {

        "author" =>  "Alice",

        "title" => "the long and windy road",

        "body" => "that leads to your door"

      }

    }



    schema.execute(mutation_string, payload)

      .should eq ({

                    "data" => {

                      "post" => {

                        "title" => "the long and windy road",

                        "body" => "that leads to your door",

                        "author" => {

                          "name" => "Alice",

                          "posts" => [

                            {

                              "title" => "the long and windy road"

                            }

                          ]

                        }

                      }

                    }

                  })

  end

end

```



### Automatic Parsing of JSON Query & Mutation Variables into InputType Structs



To ease working with input parameters custom structs can be registered to be instantiated from the json params of query and mutation requests. Given the schema from above one can define a PostInput struct as follows



```cr

struct PostInput < GraphQL::Schema::InputType

  JSON.mapping(

    author: String,

    title: String,

    body: String

  )

end

```



and register it in the schema like:



```cr

schema.add_input_type("PostInput", PostInput)

```



Now the argument `post` which is expected to be a GraphQL InputType `PostInput` will be automatically parsed into a crystal `PostInput`-struct. Thus the code in the `post` mutation callback becomes more simple:



```cr

module MutationType

  include GraphQL::ObjectType

  extend self



  field :post do |args|

    input = args["post"].as(PostInput)



    author = USERS.find &.name.==(input.author) ||

           raise "author doesn't exist"



    POSTS << Post.new(input.title, input.body, author)

    POSTS.last

  end

end

```



### Custom Context Types



Custom context types can be used to pass additional information to the object type's field resolves. An example can be found [here](spec/support/custom_context_schema.cr).



A custom context type should inherit from `GraphQL::Schema::Context` and therefore be initialized with the served schema and a max_depth.



```cr

GraphQL::Schema::Schema#execute(query_string, query_arguments = nil, context = GraphQL::Schema::Context.new(self, max_depth))

```

accepts a context type as its third argument.



Field resolver callbacks on object types (including top level query & mutation types) get called with the context as their second argument:

```cr

field :users do |args, context|

  # casting to your custom type

  # is necessary here

  context = context.as(CustomContext)

  unless context.authenticated

    raise "Authentication Error"

  end

  ...

end

```



### Serving over HTTP



For an example of how to serve a schema over a webserver([kemal](https://github.com/kemalcr/kemal)) see [kemal-graphql-example](https://github.com/ziprandom/kemal-graphql-example).



## Development



run tests with



```

crystal spec

```



## Contributing



1. Fork it ( https://github.com/ziprandom/graphql-crystal/fork )

2. Create your feature branch (git checkout -b my-new-feature)

3. Commit your changes (git commit -am 'Add some feature')

4. Push to the branch (git push origin my-new-feature)

5. Create a new Pull Request



## Contributors



- [ziprandom](https://github.com/ziprandom)  - creator, maintainer