AWS AppSync: implementing Complex Query Response Structure for Nested Data
I've searched everywhere and can't find a clear answer. I'm currently working on an AWS AppSync project using GraphQL to fetch and manipulate nested data from DynamoDB. The scenario I'm working with is related to transforming complex query responses into a format that my front-end can easily consume. Specifically, my query returns a structure that includes nested fields, but I need to flatten this structure into a more usable format for my React application. Here’s the query I’m using: ```graphql query GetUserDetails($userId: ID!) { getUser(id: $userId) { id name posts { id title comments { id content } } } } ``` The response I receive looks like this: ```json { "data": { "getUser": { "id": "1", "name": "John Doe", "posts": [ { "id": "101", "title": "Post Title 1", "comments": [ { "id": "1001", "content": "Comment 1" }, { "id": "1002", "content": "Comment 2" } ] } ] } } } ``` What I need is to restructure this response so that the comments are directly associated with the posts in a flat array. Ideally, I want something like this: ```json [ { "postId": "101", "postTitle": "Post Title 1", "comments": [ { "id": "1001", "content": "Comment 1" }, { "id": "1002", "content": "Comment 2" } ] } ] ``` I've tried using a resolver mapping template to format the response, but it seems that the complexity of the nested structure is causing issues. My current mapping template looks like this: ```vtl #set($posts = $ctx.result.getUser.posts) [ #foreach($post in $posts) { "postId": "$post.id", "postTitle": "$post.title", "comments": $post.comments }#if($foreach.hasNext),#end #end ] ``` However, when I execute the query, I get the following behavior: ``` Invalid mapping template: Invalid JSON structure. Template returns a non-JSON value. ``` I've checked that the comments array is valid, but it seems like the template might not be returning a valid JSON structure overall. Any insights on how to flatten this response correctly or fix the behavior would be greatly appreciated! This issue appeared after updating to Graphql latest. I'd be grateful for any help.