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https://astori.fr/graphql-nescala

About me

@astorije on Twitter, GitHub, …

New to Scala / GraphQL / giving talks

Ubeer

Demo time

Ubeer demo

If I were a REST API

/breweries?city=Brooklyn

[{
  "name": "Brooklyn Brewery",
  "address": "79 North Eleventh Street",
  "website": "http://www.brooklynbrewery.com/"
}]

If I were a REST API

• /breweries?city=Brooklyn → Over-fetching
• /v2/breweries?city=Brooklyn → Maintenance
• /beer/:id → Multiple round trips
• /breweries?city=Brooklyn
  /breweries&fields=name,beers.name,beers.abv
  → Custom DSL

Expected response

{
  "breweries": [{
    "name": "Brooklyn Brewery",
    "address": "79 North Eleventh Street",
    "website": "http://www.brooklynbrewery.com/",
    "beers": [{
      "name": "Black Chocolate Stout",
      "abv": 10,
      "description": "This is the famous Brooklyn […]",
      "style": {
        "name": "American-Style Stout"
      }
    }]
  }]
}

Expected response

{
  "breweries": [{
    "name": "Brooklyn Brewery",
    "address": "79 North Eleventh Street",
    "website": "http://www.brooklynbrewery.com/",
    "beers": [{
      "name": "Black Chocolate Stout",
      "abv": 10,
      "description": "This is the famous Brooklyn […]",
      "style": {
        "name": "American-Style Stout"
      }
    }]
  }]
}

GraphQL query

{
  breweries {
    name
    address
    website
    beers {
      name
      abv
      description
      style {
        name
      }
    }
  }
}

GraphQL query

{
  breweries {
    name
    address
    website
  }
}

What is GraphQL

• Query language and type system for APIs
• ∀-agnostic
• Versionless design

Let’s hack some queries

GraphiQL demo

Sangria

• Schema definition, query parsing and execution
• Translates GraphQL types to Scala types

Query Type

type Query {
  # Returns a beer
  beer(id: Int!): Beer
}

Query Type

type Query {
  # Returns a beer
  beer(id: Int!): Beer
}

{
  beer(id: 360) {
    name         
    abv          
  }              
}

Example

Query Type

val Id = Argument("id", IntType)

val QueryType = ObjectType("Query", fields[Repository, Unit](
  Field("beer", OptionType(BeerType),    
    description = Some("Returns a beer"),
    arguments = Id :: Nil,               
    resolve = c => c.ctx.beer(c.arg(Id)) 
  )                                      
))

Source

Type derivation

type Style {
  id: Int!
  name: String!
  beers: [Beer!]!
  category: Category!
}

case class Style(
  id: Int,
  category_id: Int,
  name: String
)

Source

Type derivation

val StyleType = deriveObjectType[Repository, Style](
  ObjectTypeDescription("A style of beer, […]"),
  AddFields(Field("beers", ListType(BeerType),   
    resolve = c => c.ctx.beersByStyle(c.value.id)
  )),                                            
  ReplaceField("category_id", Field("category", CategoryType,
    resolve = c => c.ctx.category(c.value.category_id).get   
  ))                                                         
)

Source

Resources

• Slides: https://astori.fr/graphql-nescala
• Demo code: https://github.com/astorije/ubeer
• GraphQL: https://graphql.org/ & https://facebook.github.io/graphql
• Sangria: https://sangria-graphql.org/
• Awesome list: https://github.com/chentsulin/awesome-graphql
• Talks:
  • GraphQL with Sangria by Oleg Ilyenko: https://youtu.be/j4q4Phsczes
  • GraphQL: Inversion of Control by Dustin Whitney: https://youtu.be/3l--XM6j-1w
  • Zero to GraphQL in 30 Minutes by Steven Luscher: https://youtu.be/UBGzsb2UkeY / https://git.io/zero-scala
• Articles
  • Sangria 1.0 by Oleg Ilyenko: https://bit.ly/2n0g19w
  • GraphQL Object Notation by Oleg Ilyenko: https://bit.ly/2mWEiww
  • The GitHub GraphQL API: https://githubengineering.com/the-github-graphql-api/