To query a list on AWS AppSync GraphQL by a nested object, you can use the GraphQL query language to specify the filter conditions for the nested object. AppSync supports complex query filtering, allowing you to retrieve items that match specific criteria within nested objects.

Let's assume you have a GraphQL schema that defines a type called Item with a nested object called nestedData. Here's an example of how you can query a list of items based on a specific property within nestedData:

GraphQL Schema:

graphql
type Item { id: ID! name: String! nestedData: NestedData! } type NestedData { nestedField: String! }

GraphQL Query to Retrieve Items Based on a Nested Property:

graphql
query GetItemsByNestedField($nestedField: String!) { getItemsByNestedField(nestedField: $nestedField) { items { id name nestedData { nestedField } } } }

In this query, we're using a custom resolver function called getItemsByNestedField, which takes a parameter nestedField of type String!. The resolver function is responsible for filtering the list of items based on the nestedField property in the nestedData object.

You'll need to implement the resolver function on the server side (e.g., using AWS Lambda, DynamoDB, or another data source) to perform the filtering based on the provided nestedField. The resolver function should return the list of items that match the filter criteria.

For example, if you're using AWS Lambda as the data source, the resolver function might look like this (using Node.js):

javascript
// Sample resolver function (using AWS Lambda and DynamoDB) exports.handler = async (event) => { const { nestedField } = event.arguments; // Perform the filtering based on the nestedField using DynamoDB or any other data source const filteredItems = await getItemsByNestedFieldFromDynamoDB(nestedField); return { items: filteredItems, }; };

Remember to configure your AWS AppSync API to use this resolver function for the getItemsByNestedField query.

In your frontend application, you can use the AWS Amplify library or any GraphQL client to send the query and retrieve the filtered list of items.

Keep in mind that the specific implementation of the resolver function and data source may vary based on your backend setup and requirements. The provided example is a basic illustration of how you can query a list on AWS AppSync GraphQL by a nested object.

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