Now you’ve deployed your smart contracts (or plan on using existing ones), you’re ready to connect to them in your application. The /application directory contains a /const directory, which has two files:
  1. chains.ts: Define the testnet and mainnet chains your smart contracts are deployed to.
  2. contracts.ts: Define the addresses of your smart contracts on each chain.
Configure these files to connect to your smart contracts.

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Configuring Chains

The application assumes you have two separate environments. One for testing purposes and one for production. You can choose to use separate chains for each environment, or simply use the same chain for both. All you need to do is configure the DEVELOPMENT_CHAIN and PRODUCTION_CHAIN variables to your chosen chains, and you’re good to go. By default, the application uses the Polygon Mumbai test network for testing and the Polygon Mainnet network for production:
Example: Use Mumbai for testing and Polygon for production
import { Polygon, Mumbai } from "@thirdweb-dev/chains";

export const IS_DEV_ENV = process.env.NODE_ENV === "development";

const DEVELOPMENT_CHAIN = Mumbai; // e.g. Mumbai used for local development
const PRODUCTION_CHAIN = Polygon; // e.g. Polygon used for production

export const CHAIN = IS_DEV_ENV ? DEVELOPMENT_CHAIN : PRODUCTION_CHAIN;
The IS_DEV_ENV detects whether you’re running the application in a development environment or not. The CHAIN variable uses that value to return your chosen development chain in development and your chosen production chain in production.

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Configuring Contract Addresses

The contracts.ts file is where you put the addresses of your smart contracts. For each smart contract you want to connect to, you can follow the same pattern below:
  1. Define a variable containing the testnet address of your smart contract.
  2. Define a variable containing the mainnet address of your smart contract.
  3. Export a variable that returns the testnet address in development and the mainnet address in production (and cast it as the test network address’s type).
const greeter_dev = "0x2E74A1664dA1066FFa4aF8b85856cb474D189029"; // e.g. Mumbai
const greeter_prod = "0x123456789123456789123456789123456789123"; // e.g. Polygon

// Export this to use as the address of your smart contract throughout the app.
export const greeter = IS_DEV_ENV
  ? greeter_dev // Will be the test network address in development
  : (greeter_prod as typeof greeter_dev); // and main network address in production
No smart contract ABI is required when using the thirdweb React SDK; it is either fetched at run-time or pulled from the generation process.

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Generating Contract Types

Since we don’t copy smart contract ABIs into the application; our IDE doesn’t know what functions, views, events, etc. are available on each smart contract. Without this, we don’t get any help from our IDE when interacting with smart contracts. The thirdweb CLI comes with a generate command, which detects all smart contract addresses in the project and fetches their ABIs, pulling them into node_modules to enable type-safety on smart contract interactions like useContractRead and useContractWrite.
If you prefer, you can just provide the contract ABIs as the second argument to useContract to achieve the same effect of type-safety and performance gains.
To get this type-safety, run yarn generate from the application directory. This will create a thirdweb.json file at the root of your app; which you can modify and re-run yarn generate to pull in new ABIs, or update existing ones. 
yarn generate
For example, running yarn generate with the below configuration inside thirdweb.json will pull in the ABI for the 0x2E7 smart contract on the Polygon Mumbai test network:
thirdweb.json
{
  "chainIds": [
    80001
  ],
  "contracts": [
    {
      "address": "0x2E74A1664dA1066FFa4aF8b85856cb474D189029",
      "chainId": 80001
    }
  ]
}
After running generate, smart contract interactions become type-safe as the ABIs are now available to the IDE. It also provides a performance increase as the function doesn’t need to fetch the ABI at run-time.
Sometimes, you might need to restart the TypeScript server for the IDE to pick up the new types.
ABIs can be found in the /node_modules/@thirdweb-dev/generated-abis/dist directory.

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Contract Interactions

Now you have set up your chains, contract addresses, and generated your contract types, you can start interacting with your smart contracts. The application comes with an example ContractInteraction component to showcase the useContract, useContractRead and useContractWrite hooks from thirdweb’s React SDK. For smart contracts that follow EIP standards, there is a range of other hooks such as useNFT documented in thirdweb’s React SDK.
thirdweb’s hooks are powered by TanStack Query.Read my blog post on TanStack Query for a quick introduction.

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Reading Data

For generic smart contract reads, you can use the useContractRead hook. 
const { data, isLoading, error } = useContractRead(contract, "functionName");

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Writing Data

For initiating transactions, you can use the useContractWrite hook, and the Web3Button to ensure the user has a connected wallet and is on the correct chain. 
const { mutateAsync, isLoading } = useContractWrite(contract, "functionName");