dotansimha / codegen-resolvers-example

GraphQL Codegen example for generating MongoDB resolvers from GraphQL scheme

GraphQL Codegen example for generating MongoDB resolvers from GraphQL scheme

Overview

This example uses GraphQL Code Generator custom templates feature, to generate GraphQL resolvers based on the GraphQL schema, using MongoDB.

How to run?

1. Start by cloning this project, then run yarn to install the project's dependencies.
2. Generate the resolvers code according to your GraphQL Schema by running yarn generate
3. Execute the server by running yarn start
4. Open GraphiQL (default to: http://localhost:3000/graphiql) to test the GraphQL endpoint.

How it works?

The schema defines a custom GraphQL Directives to declare links, mapping and DB object structure between the GraphQL schema entites, then, using a custom GraphQL Code Generator template, we generate a custom TypeScript file with a resolver, that access the DB and fetches the data.

Available Directives

These directives are available in this example:

• @resolvers - decalres that this GraphQL type is a root type, and it's fields and plain queries (put it over Query type)

• @query - goes with GraphQL field inside a type with @resolvers: declares the query that needed to be executed (including skip, limit and custom MongoDB cursor)

• @entity - declares that this GraphQL type comes the the DB, and the generator should generate Type resolvers for it

• @map - goes with GraphQL field inside a type with @entity: declare the mapping between the MongoDB field to GraphQL field, for example id -> _id

• @util - goes with GraphQL field inside a type with @entity: declares either a context function to execute or a simple MomentJS formating for Date

• @link - goes with GraphQL field inside a type with @entity: declares a MongoDB query that needed to execute in order to fetch the object, use it for table links

See src/typedefs/schema.ts for the GraphQL definitions and GraphQL Schema.