Make a user object property resolved inside #FieldResolver (posts) - node.js

Question

I am creating a reddit clone, using a type-graphql, express-graphql and typegoose,
first i run a query for posts and i get the user info (_id, username) :
query posts {
posts {
_id
title
image
body
user {
_id
username
}
subredditList {
topic
_id
}
createdAt
}
}
but when i run query for subreddit to get all posts that belong to that subreddit, i get a user is null
the query i run for subreddit:
query subreddit($topic: String!) {
subreddit(input: { topic: $topic }) {
_id
topic
posts {
_id # works fine
title # works fine
body # works fine
image # works fine
# the user is null !!, i get user: null
user {
_id
username
}
createdAt
}
}
}
I get user: null even when the posts field in Subreddit object type is resolved
Subreddit object type:
#ObjectType()
export class Subreddit {
#Field(() => String)
_id: string;
#Field(() => String)
#prop({ required: true })
topic: string;
#Field(() => [Post])
posts: Post[]; // i get all info exept the user object
#Field(() => String)
createdAt: string;
#Field(() => String)
updatedAt: string;
}
Subreddit resolver:
#Resolver(() => Subreddit, {})
export default class SubredditResolver {
constructor(private readonly subredditService: SubredditService) {
this.subredditService = new SubredditService();
}
#Query(() => [Subreddit])
async subreddits() {
return this.subredditService.subreddits();
}
#Query(() => Subreddit, { nullable: true })
async subreddit(#Arg("input") input: GetSubredditByTopic) {
return this.subredditService.subreddit(input);
}
#Mutation(() => Subreddit)
async createSubreddit(
#Arg("input") input: CreateSubredditInput
): Promise<Subreddit> {
return this.subredditService.createSubreddit(input);
}
// here where i resolve the "posts" field in my Subreddit object type
#FieldResolver(() => Post, {})
async posts(#Root() subreddit: Subreddit) {
console.log(args);
return this.subredditService.posts(subreddit);
}
}
and finally the resolver function is like this:
async posts(input: Subreddit) {
try {
const posts = await PostModel.find({ subredditId: input._id });
return posts;
} catch (err) {
console.log(err);
throw new Error("Couldn't get the posts");
}
}
Here is my Post object type looks like:
#ObjectType()
export class Post {
#Field(() => String)
_id: string;
#Field(() => String)
#prop({ required: true })
title: string;
#Field(() => String)
#prop({ required: true })
body: string;
#Field(() => String, { nullable: true })
#prop({})
image: string;
#Field(() => String)
#prop({ ref: () => Subreddit })
subredditId: Ref<Subreddit>;
#Field(() => [Subreddit])
subredditList: [Subreddit];
#Field(() => [Comment])
comments: Comment[];
// note that the "user" field is string refers to id of the user,
#Field(() => User, { nullable: true })
#prop({ ref: () => User })
user: Ref<User>;
#Field(() => Date)
createdAt: Date;
#Field(() => Date)
updatedAt: Date;
}
Post resolver:
#Resolver(() => Post)
export default class PostResolver {
constructor(private readonly postService: PostService) {
this.postService = new PostService();
}
#Query(() => [Post])
async posts() {
return this.postService.posts();
}
#Authorized()
#Mutation(() => Post)
async createPost(
#Arg("input") input: CreatePostInput,
#Ctx() context: Context
): Promise<Post> {
return this.postService.createPost(input, context);
}
#FieldResolver()
async subredditList(#Root() post: Post) {
return this.postService.subredditList(post);
}
// here i resolve the user field in my Post object type, and it works fine
#FieldResolver()
async user(#Root() post: Post) {
return this.postService.user(post);
}
}
the resolver function for "user" field in Post object type:
async user(input: Post) {
try {
const user = await UserModel.findOne({
_id: input.user,
}).lean();
return user;
} catch (err) {
console.log(err);
throw new Error("Couldn't get the user");
}
}
the property "user" from post query is resolved but when i run subreddit query i get user is null .
any help please ?
thanks in advance.

Answer 1

Your problem seems to be that you are missing setting the type for arrays, like:
class YourClass {
// ...
#Field(() => [Post])
posts: Post[];
// ...
}
but it would need to be like:
class YourClass {
// ...
#Field(() => [Post])
#prop({ type: () => [Post] })
posts: Post[];
// ...
}
see Quick-Start-Guide
type has to be defined when working with Arrays, because Reflection only returns basic information. Look here for why
Like public: string[] is in reflection only Array.
or the note in #prop: Array Options
Option type must be provided, otherwise the array will result in Mixed read typegoose issue #300 for more info
Note: i dont know if anything is wrong with your graphql setup
i also read in the comments that there is supposedly a _doc property, which is internal in mongoose and should never be shown, but it gets exposed instead of properly translated due to a problem with class-transformer, the only workaround is to use #Exclude() for the whole class (or globally) and only #Expose() the proper properties, also see Integration Examples: Using with class-transformer