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IndexerClient Class

The IndexerClient is responsible for handling the communication between the client-side application and the blockchain network. It uses the Hasura framework to generate a set of GraphQL queries that can be used to retrieve data from the blockchain. The queries are optimized for performance and can retrieve data in real-time.

Usage​

To use the IndexerClient class, you will need to create an instance of IndexerClient and call the desired API method. The IndexerClient object will handle the HTTP requests and responses and return the result to your application.

Configuration​

Before using the IndexerClient class, you will need to configure it with the necessary parameters. These parameters may include the Hasura endpoint URL, custom configuration, and any other required settings. You can configure the IndexerClient class by passing in the necessary parameters when you initialize the client object.

Initialization​

To initialize the IndexerClient class, you will need to pass in the necessary configuration parameters. Here is an example:

import { IndexerClient } from "aptos";

const client = new IndexerClient(
  "https://api.testnet.aptoslabs.com/v1/graphql",
);

Make API fetch calls​

To make an API call, you will need to call the appropriate method on the IndexerClient object. The method name and parameters will depend on the specific API you are using. Here is an example:

const accountNFTs = await client.getAccountNFTs("0x123");

In this example, we are using the getAccountNFTs() method to retrieve the NFT of an account with the address 0x123.

Use custom queries​

The TypeScript SDK provides frequently used queries by different users and/or apps and makes sure the queries are well-structured to retrieve the current response.

With that being said, one can structure custom queries and use the SDK to query the Aptos Indexer API. For that, the SDK exports a queryIndexer() method that accepts a GraphqlQuery type argument. The GraphqlQuery type has a query field of type string and an optional variable field of an object type.

Here is the GraphqlQuery type definition.

type GraphqlQuery = {
  query: string;
  variables?: {};
};

To use the queryIndexer() method, one should pass the GraphQL query. For example:

const query: string = `query getAccountTokensCount($owner_address: String) {
  current_token_ownerships_aggregate(where: { owner_address: { _eq: $owner_address }, amount: { _gt: "0" } }) {
    aggregate {
      count
    }
  }
}`;
const variables = { owner_address: "0x123" };
const graphqlQuery = { query, variables };
const accountTokensCount = await client.queryIndexer(graphqlQuery);
tip

Be aware that it queries the network endpoint you passed in when initializing the IndexerClient class.

Generate queries​

To generate an Indexer query that can be used within the SDK, we can write a GraphQL query (based on the Indexer schema) and use the SDK to generate a TypeScript query.

Write an Indexer query​

All Indexer queries, which are basically GraphQL queries, live under the src/indexer/queries/ folder. In this folder, we create a .graphql file for each query we want the SDK to support. For example, a .graphql file with a GraphQL query can be:

query getAccountTokensCount($owner_address: String) {
  current_token_ownerships_aggregate(
    where: { owner_address: { _eq: $owner_address }, amount: { _gt: "0" } }
  ) {
    aggregate {
      count
    }
  }
}

Generate TypeScript queries​

Once we have created a .graphql file with a GraphQL query, we can generate TypeScript code based on that query, so we can use it with the TypeScript SDK by running the following command:

pnpm run indexer-codegen

That command runs the graphql-codegen command that generates code from the Indexer GraphQL schema based on the SDK configuration file.

SDK GraphQL configuration file​

The TypeScript SDK uses a configuration file for @graphql-codegen, a code generation tool for GraphQL.

The SDK configuration file defines how @graphql-codegen should generate TypeScript code from a GraphQL schema and queries. Let's break down some of the key elements of this file:

  • schema – Specifies the location of the GraphQL schema file that @graphql-codegen should use for code generation. In this case, it is using the Aptos Indexer mainnet schema.
  • documents - Specifies the location of the GraphQL operation files that @graphql-codegen should use for code generation. In this case, it is using the src/indexer/queries/ location (as mentioned in the previous section) and includes all files with the .graphql extension.
  • generates – Defines the output files that @graphql-codegen should generate based on the schema and operations. In this case, it is generating the types, operations and queries.
  • plugins – Specifies the plugins that @graphql-codegen should use for code generation. In this case, it is using the typescript plugin to generate TypeScript typings from the GraphQL schema, typescript-operations plugin to generate TypeScript typings for GraphQL operations and typescript-graphql-request plugin to generate function for making GraphQL requests .
tip

You can use the IndexerClient class directly or the Provider class (preferred).