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Generate a contract factory

What is a contract factory?

In the Zapper API, a ContractFactory class is a convenience helper class that instantiates typed Ethers.js contract instances. These contracts require having the ABI defined in your app subdirectory. We use TypeChain to automatically generate types for these ABIs to simplify the developer experience of interacting with smart contracts.

Add an ABI to your app

For the Pickle Finance app, we'll need the ABI for the Jar tokens that we intend to enumerate in our application. An easy way to find this ABI is to open any Pickle vault token on Etherscan, click the Contract tab, scroll down, and copy the JSON from the Contract ABI section.

Copy the ABI

Once copied, we'll save the JSON in src/apps/pickle/contracts/abi/pickle-jar.json.

We'll need the same for any Pickle farm on Etherscan. Save the ABI from here to src/apps/pickle/contracts/abi/pickle-gauge.json.

Generate the contract factory class

In your terminal, run pnpm studio generate:contract-factory pickle. This command will generate TypeChain interfaces for all contract ABIs you have in the src/apps/pickle/contracts/abi directory, and generate our injectable PickleContractFactory convenience class in src/apps/pickle/contracts/index.ts.

Generate Factory

If you add more ABIs in the future, simply save the JSON in the abis directory like in the previous step, and re-run the CLI script to regenerate the contract factory and types.

We're done here! In the next section, we'll use this contract to list out Pickle jar tokens in our application.