Assign interface type to code-first GraphQL resolver argument

Question

The following code-first GraphQL schema example is taken from GraphQL's Constructing Types page.

// Define the Query type
var queryType = new graphql.GraphQLObjectType({
  name: 'Query',
  fields: {
    user: {
      type: userType,
      // `args` describes the arguments that the `user` query accepts
      args: {
        id: { type: graphql.GraphQLString }
      },
      resolve: (_, {id}) => {
        return fakeDatabase[id];
      }
    }
  }
});

Although you are able to define the args and their GraphQL types (GraphQLString in this example), the actual id property within the resolver has an "any" type.

I tried replacing {id} with {id}: {id: string} but that threw the error Type '(_: any, { id }: { id: string; })' is not assignable to type 'GraphQLFieldResolver<any, any, { [argName: string]: any; }>' Type '(_: any, { id }: { id: string; })' is not assignable to type 'GraphQLFieldResolver<any, any, { [argName: string]: any; }>' .

Although this is a simple "string" example, my actual code has more complex object types with multiple properties. Ensuring the correct property name is referenced is a big help elsewhere that is missing within the resolvers. Perhaps there is a way to tell the resolver the actual types of the args but I'm too new to TypeScript to find it.

Is there a way to define/override the types of the resolvers args?

Answer 1

I believe you are having the same problem outlined in this issue .

A workaround is to make your id property optional (by replacing {id} with {id}: {id?: string} ) and check for its existence within the resolver before you reference it.