NestJs：根据外部 API 调用返回修改后的响应

Question

I am new to NestJs, Graphql, typescript.

I need to make an external API call which is basically Graphql query itself, modify the response if needed and return the response for the original request/query in this case test which is the query name.

I have the following code

@Query(returns => BlogPost) // @objectType
  async test() {
    const endpoint = 'https://testing.org/api/content/project-dev/graphql' 
    const graphQLClient = new GraphQLClient(endpoint, {
      headers: {
        authorization: 'Bearer xxxx',
      },
    })
    const query = gql`
      {
        queryContentContentsWithTotal(top: 10) {
          total
        }
      }`

    const data = await graphQLClient.request(query)
    console.log(JSON.stringify(data, undefined, 2))
    return data;
  }

The BlogPost is the ObjectType which looks like:

import { Field, ObjectType } from '@nestjs/graphql';

@ObjectType()
export class BlogPost {
  @Field({ nullable: true })
  total!: number;
}

I have placed console.log as well to see the external API call response which is:

{
  "queryContentContentsWithTotal": {
    "total": 1
  }
}

but the Graphql response for the query is:

{
  "data": {
    "test": {
      "total": null // this needs to be 1 
    }
  }
}

total is null where the API call returns total value 1;

How can be the mapping done with flexibility here so that the query response looks the same?

Answer 1

GraphQL is expecting your return data in the shape of

{
  "total": "number of some sort"
}

But you're actually returning data in the shape of

{
  "queryContentContentsWithTotal": {
    "total": 1
  }
}

So the GraphQL engine can't understand the return type. You need to map your data to the proper return like so:

@Query(returns => BlogPost) // @objectType
  async test() {
    const endpoint = 'https://testing.org/api/content/project-dev/graphql' 
    const graphQLClient = new GraphQLClient(endpoint, {
      headers: {
        authorization: 'Bearer xxxx',
      },
    })
    const query = gql`
      {
        queryContentContentsWithTotal(top: 10) {
          total
        }
      }`

    const data = await graphQLClient.request(query)
    console.log(JSON.stringify(data, undefined, 2))
    return data.queryContentContentsWithTotal;
  }

Answer 2

You are returning data which is not the same type as BlogPost . You should return this instead

return {total: data.queryContentContentsWithTotal.total}