# GraphQL

GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools.

# Feature

# Apollo

# Installation

    import {Configuration} from "@tsed/common";
    import "@tsed/platform-express";
    import "@tsed/apollo";
    import {join} from "path"
    
    @Configuration({
      apollo: {
        "server1": {
          // GraphQL server configuration
          path: "/",
          // apollo-server-express
          // installSubscriptionHandlers?: boolean;
          // Give custom server instance
          // server?: (config: Config) => ApolloServer; 
    
          // ApolloServer options
          // ...
          // See options descriptions on https://www.apollographql.com/docs/apollo-server/api/apollo-server.html
        }
      }
    })
    export class Server {
    }
    
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    # Nexus

    # Installation

      Now, we can configure the Ts.ED server by importing @tsed/apollo in your Server:

      import {Configuration} from "@tsed/common";
      import "@tsed/platform-express";
      import "@tsed/apollo";
      import {schema} from "./schema"
      import {join} from "path"
      
      @Configuration({
        apollo: {
          "server1": {
            // GraphQL server configuration
            path: "/",
            schema
            // apollo-server-express
            // installSubscriptionHandlers?: boolean;
            // Give custom server instance
            // server?: (config: Config) => ApolloServer; 
      
            // ApolloServer options
            // ...
            // See options descriptions on https://www.apollographql.com/docs/apollo-server/api/apollo-server.html
          }
        }
      })
      export class Server {
      }
      
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      Then create schema/index.ts:

      import { makeSchema } from 'nexus'
      import { join } from 'path'
      
      export const schema = makeSchema({
        types: [], // 1
        outputs: {
          typegen: join(__dirname, '..', '..', 'nexus-typegen.ts'), // 2
          schema: join(__dirname, '..', '..', 'schema.graphql'), // 3
        }
      });
      
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      # TypeGraphQL

      # Installation

      To begin, install the @tsed/typegraphql package:

        Now, we can configure the Ts.ED server by importing @tsed/typegraphql in your Server:

          # Types

          We want to get the equivalent of this type described in SDL:

          type Recipe {
            id: ID!
            title: String!
            description: String
            creationDate: Date!
            ingredients: [String!]!
          }
          
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          So we create the Recipe class with all properties and types:

          class Recipe {
            id: string;
            title: string;
            description?: string;
            creationDate: Date;
            ingredients: string[];
          }
          
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          Then we decorate the class and its properties with decorators:

          import {Field, ID, ObjectType} from "type-graphql";
          
          @ObjectType()
          export class Recipe {
            @Field(type => ID)
            id: string;
          
            @Field()
            title: string;
          
            @Field({nullable: true})
            description?: string;
          
            @Field()
            creationDate: Date;
          
            @Field(type => [String])
            ingredients: string[];
          }
          
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          The detailed rules for when to use nullable, array and others are described in fields and types docs (opens new window).

          # Resolvers

          After that we want to create typical crud queries and mutation. To do that we create the resolver (controller) class that will have injected RecipeService in the constructor:

          import {Inject} from "@tsed/di";
          import {ResolverService} from "@tsed/graphql";
          import {Arg, Args, Query} from "type-graphql";
          import {RecipeNotFoundError} from "../errors/RecipeNotFoundError";
          import {RecipesService} from "../services/RecipesService";
          import {Recipe} from "../types/Recipe";
          import {RecipesArgs} from "../types/RecipesArgs";
          
          @ResolverService(Recipe)
          export class RecipeResolver {
            @Inject()
            private recipesService: RecipesService;
          
            @Query(returns => Recipe)
            async recipe(@Arg("id") id: string) {
              const recipe = await this.recipesService.findById(id);
              if (recipe === undefined) {
                throw new RecipeNotFoundError(id);
              }
          
              return recipe;
            }
          
            @Query(returns => [Recipe])
            recipes(@Args() {skip, take}: RecipesArgs) {
              return this.recipesService.findAll({skip, take});
            }
          }
          
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          # Data Source

          Data source is one of the Apollo server features which can be used as option for your Resolver or Query. Ts.ED provides a DataSourceService decorator to declare a DataSource which will be injected to the Apollo server context.

          import {DataSourceService} from "@tsed/graphql";
          import {RESTDataSource} from "apollo-datasource-rest";
          import {User} from "../models/User";
          
          @DataSourceService()
          export class UserDataSource extends RESTDataSource {
            constructor() {
              super();
              this.baseURL = "https://myapi.com/api/users";
            }
          
            getUserById(id: string): Promise<User> {
              return this.get(`/${id}`);
            }
          }
          
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          Then you can retrieve your data source through the context in your resolver like that:

          import {ResolverService} from "@tsed/graphql";
          import {Arg, Authorized, Ctx, Query} from "type-graphql";
          import {UserDataSource} from "../datasources/UserDataSource";
          import {User} from "../models/User";
          
          @ResolverService(User)
          export class UserResolver {
            @Authorized()
            @Query(() => User)
            public async user(
              @Arg("userId") userId: string,
              @Ctx("dataSources") dataSources: any
            ): Promise<User> {
              const userDataSource: UserDataSource = dataSources.userDataSource;
          
              return userDataSource.getUserById(userId);
            }
          }
          
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          # Get Server instance

          ApolloService (or TypeGraphQLService) lets you to retrieve an instance of ApolloServer.

          import {Inject, AfterRoutesInit, Injectable} from "@tsed/common";
          import {ApolloService} from "@tsed/apollo";
          import {ApolloServer} from "apollo-server-express";
          
          @Injectable()
          export class UsersService implements AfterRoutesInit {
            @Inject()
            private ApolloService: ApolloService;
            // or private typeGraphQLService: TypeGraphQLService;
          
            private server: ApolloServer;
          
            $afterRoutesInit() {
              this.server = this.apolloService.get("server1")!;
            }
          }
          
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          For more information about ApolloServer, look at its documentation here (opens new window);

          # Testing

          Here is an example to create a test server based on TypeGraphQL and run a query:

          The unit example is also available to test any Apollo Server!

            # Author

              # Maintainers

                Last Updated: 6/19/2021, 2:43:17 PM

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