All You Ever Wanted To Know About GraphQL

Accompanying Github repo: https://github.com/takeshape/jamstack-meetup-graphql-demo

What is GraphQL?

Schema Definition + Query language + Resolution framework

Schema

• Provides a strongly typed description of your data
• Schema Description Language (SDL) is the recommended cross-platform way to specify schema.

enum Title {
    ACTOR
    DIRECTOR
}

type Role {
    characterName: String!
    title: Title
    movie: Movie
}

type Person {
    name: String!
    photo: String
    filmography: [Role]
}

type Movie {
    title: String!
    watched: Boolean
    rating: Float
    poster: String
    actors: [Person]!
    director: Person!
    year: String
}

GraphQL Schema also specifies how you interact with your data with queries and mutations

type Query {
    listMovies: [Movie]
}

type Mutation {
    addMove(title: String): [Movie]
    removeMovie(title: String): [Movie]
}

Query Langauge

Query your data and fetch exactly what you need

query {
    getToWatchList {
        watched
        movie {
            title
            year
            director
        }
    }
}

{
  "data": {
    "getToWatchList": [
      {
        "watched": true,
        "movie": {
          "title": "Top Gun",
          "year": "1985",
          "director": "Tony Scott"
        }
      },
      {
        "watched": true,
        "movie": {
          "title": "Big Trouble in Little China",
          "year": "1986",
          "director": "John Carpenter"
        }
      },
      {
        "watched": true,
        "movie": {
          "title": "The Princess Bride",
          "year": "1987",
          "director": "Rob Reiner"
        }
      },
      {
        "watched": false,
        "movie": {
          "title": "Taxi Driver",
          "year": "1976",
          "director": "Martin Scorsese"
        }
      }
    ]
  }
}

Mutations

Modify your data

mutation {
    addMovieToWatch(title: "Die Hard") {
        watched
        movieTitle
        movie {
            title
            year
            director
        }
    }
}

{
  "data": {
    "addMovieToWatch": [
      {
        "watched": false,
        "movie": {
          "title": "Taxi Driver",
          "year": "1976",
          "director": "Martin Scorsese"
        }
      },
      {
        "watched": false,
        "movie": {
          "title": "Die Hard",
          "year": "1988",
          "director": "John McTiernan"
        }
      }
    ]
  }
}

Resolution Framework

• Each GraphQL implementation provides it own query resolution framework
• GraphQL.js is the reference implementation
• Perform query and mutation resolution

Schema (SDL)

type Query {
    getToWatchList: [ToWatch]
}

type Mutation {
    addMovieToWatch(title: String!): [ToWatch]
    removeMovieToWatch(title: String!): [ToWatch]
    markMovieWatched(title: String! watched: Boolean!): [ToWatch]
}

Resolvers

const resolvers = {
    Query: {
        getToWatchList: () => {
            return WatchList.list();
        }
    },
    
    Mutation: {
        addMovieToWatch(_, {title}) {
            return WatchList.add(title);
        },

        removeMovieToWatch(_, {title}) {
            return WatchList.remove(title);
        },

        markMovieWatched(_, {title, watched}) {
            return WatchList.markWatched(title, watched);
        }
    }
};

Resolvers are also able to resolve dynamically computed fields

Schema (SDL)

type Move {
    title: String
    rating: Float
    poster: String
    actors: String
    director: String 
    year: String
}

type ToWatch {
    movieTitle: String!
    movie: Movie
    watched: Boolean!
}

Resolvers

const resolvers = {
    ToWatch: {
        async movie(toWatch) {
            const info = await fetchMovieInfo(toWatch.movieTitle);
            return info ? {
                title: info.Title,
                rating: info.imdbRating,
                poster: info.Poster,
                year: info.Year,
                actors: info.Actors,
                director: info.Director
            } : null
        }
    }
};