'GraphQL Expected Iterable, but did not find one for field xxx.yyy

I'm currently trying GraphQL with NodeJS and I don't know, why this error occurs with the following query:

{
  library{
    name,
    user {
      name
      email
    }
  }
}

I am not sure if the type of my resolveLibrary is right, because at any example I had a look at they used new GraphQL.GraphQLList(), but in my case I really want to return a single user object, not an array of users.

My code:

const GraphQL = require('graphql');
const DB = require('../database/db');
const user = require('./user').type;

const library = new GraphQL.GraphQLObjectType({
    name: 'library',
    description: `This represents a user's library`,
    fields: () => {
        return {
            name: {
                type: GraphQL.GraphQLString,
                resolve(library) {
                    return library.name;
                }
            },
            user: {
                type: user,
                resolve(library) {
                    console.log(library.user);
                    return library.user
                }
            }
        }
    }
});

const resolveLibrary = {
    type: library,
    resolve(root) {
        return {
            name: 'My fancy library',
            user: {
                name: 'User name',
                email: {
                    email: '[email protected]'
                }
           }
        }
    }
}

module.exports = resolveLibrary;

Error:

Error: Expected Iterable, but did not find one for field library.user.

So my library schema provides a user field which returns the right data (the console.log is called).

node.jsgraphqlgraphql-js


Solution 1:[1]

I ran into this problem as well. It appears that what you're returning from your resolver doesn't match the return type in your schema.

Specifically for the error message Expected Iterable, but did not find one for field library.user., your schema expects an array(Iterable) but you aren't returning an array in your resolver

I had this in my schema.js:

login(email: String, password: String): [SuccessfulLogin]

I changed that to:

login(email: String, password: String): SuccessfulLogin

Notice the square brackets around "SuccessfulLogin". It's up to you whether you want to update the resolver return type or update the schema's expectations

Solution 2:[2]

I guess your user is an instance of GraphQLList that is why the field user is expecting to resolve to an iterable object.

Solution 3:[3]

I had the same problem. I was using find instead filter.

Solution 4:[4]

I ran into the same issue but i was using GraphQL with Go.

Solution: I mentioned the return type to be a list( or you can say an array), but my resolver function was returning an interface and not a list of interfaces.

Before it was =>

Type: graphql.NewList(graphqll.UniversalType)

Later i changed it to =>

Type: graphqll.UniversalType

graphqll.UniversalType : 'graphqll' is the name of my user-defined package and 'UniversalType' is the GraphQL object i have created.

The previous structure of graphql object was :

var GetAllEmpDet = &graphql.Field{
    Type: graphql.NewList(graphqll.UniversalType),
    Resolve: func(params graphql.ResolveParams) (interface{}, error) {
       ...
       ...
       // Your resolver code goes here, how you handle.
       ...
       return models.Universal, nil // models.Universal is struct and not list of struct so it gave that error.
    },
}

It worked when i changed this to:

var GetAllEmpDet = &graphql.Field{
    Type: graphqll.UniversalType,
    Resolve: func(params graphql.ResolveParams) (interface{}, error) {
       ...
       ...
       // Your resolver code goes here, how you handle.
       ...
       return models.Universal, nil // models.Universal is struct and not list of struct so it gave that error.
    },
}

Solution 5:[5]

In my case it was related to django-graphene I didn't have a resolve method defined.

class SomeNode(DjangoObjectType):
    things = graphene.List(ThingNode)

    def resolve_things(self, info, **kwargs):
        return self.things.all()

Solution 6:[6]

For me, it was a simple fix.

 items: {
        type: new GraphQLList(VideoType),<-- error
        resolve(parentValue, args) {
            const url = 'www'

            return axios.get(url)
                .then(res => res.data);
        }
    }

and change it to

 items: {
        type: VideoType,
        resolve(parentValue, args) {
            const url = 'www'

            return axios.get(url)
                .then(res => res.data);
        }
    }

Solution 7:[7]

I faced the same issue. For me, it was an issue with Mongo DB model.js file.

GraphQL kept throwing that error because my model was saving the field as an object whereas graphQL was returning it as an array. The code that caused the error was this.

tableHeaders: {
            
              text: {
                type: String,
                required: false,
              },
              align: {
                type: String,
                required: false,
              },
              sortable: {
                type: Boolean,
                required: false,
              },
              value: {
                type: String,
                required: false,
              },
            
          },

It was corrected to the following.

tableHeaders: [
            {
              text: {
                type: String,
                required: false,
              },
              align: {
                type: String,
                required: false,
              },
              sortable: {
                type: Boolean,
                required: false,
              },
              value: {
                type: String,
                required: false,
              },
            },
          ],

Changing type from object to array fixed it.

Solution 8:[8]

It's usually a simple mistake. Caused by declaring in the schema a List instead of a Field. The reverse will happen if you interchange. An example from Django-graphene. Switch from this:

my_query_name = graphene.List(MyModelType, id=graphene.Int())

to this:

my_query_name = graphene.Field(MyModelType, id=graphene.Int())

Solution 9:[9]

i had the same issue i was using findOne and that seems like the issue that didnt worked. i changed to find and it worked

    @Query(()=> [Post])
    async getSinglePost(
        @Arg('post_id') id: string,
    ){
        /*
        const post = await getConnection().getRepository(Post).findOne({uuid:postuid})
        console.log(post);
        return post
        */

        const post = Post.find({uuid:id})
        return post
    }

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 PCDSandwichMan
Solution 2 Uziel Valdez
Solution 3 Alfrex92
Solution 4
Solution 5 jmunsch
Solution 6 John Fleurimond
Solution 7
Solution 8 Musili
Solution 9 Stanley Coffey

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