Is the intended use of the Factory non-type .ts file documented?

I’m curious what the purpose of the ...Factory.ts file is in a project like this:

types/Greeter.d.ts
types/GreeterFactory.ts
types/index.d.ts

Is that documented somewhere? I’m not sure if this question is ethers-specific or not. Thanks!

[quezak]

I’ve added a simple readme including what I’ve wrote above plus some basic info about contract type declarations. Thanks @pcowgill for the suggestion!

[quezak]

Yes. I’ll write a short overview here, @pcowgill please tell us what should be described more.

The factory classes are an extension of ethers’ ContractFactory. They serve two main purposes:

• wrap passing contract ABI and bytecode to the ContractFactory class, so you don’t have to load and parse the JSON manually
• provide a correctly typed interface to ContractFactory (since it returns plain Contract instances).

Another case are abstract contracts or solidity interfaces, because they have no bytecode. For those, a simplified factory is generated that doesn’t extends ContractFactory, and only includes the static connect method, so you can easily connect to a deployed instance without having to pass the ABI manually.

Very simple example:

// suppose you have an `Erc20Token` solidity interface and a `DummyToken` contract implementing it

import { BigNumber } from 'ethers/utils';
import { Wallet } from 'ethers';

import { DummyTokenFactory } from '@contracts/DummyTokenFactory';
import { DummyToken } from '@contracts/DummyToken';
import { Erc20TokenFactory } from '@contracts/Erc20TokenFactory';

const provider = getYourProvider(...);

// use the concrete contract factory if you need to operate on the bytecode (ie. deploy)
async function deployTestToken(ownerPK: string): Promise<DummyToken> {
    const owner = new Wallet(ownerPK, provider);
    return new DummyTokenFactory(owner).deploy();
}

// to call existing contracts, a factory for both the concrete contract and for the interface
// can be used since the ABI is the same
async function getTokenBalance(walletAddress: string, tokenAddress: string): Promise<BigNumber> {
    const token = Erc20TokenFactory.connect(tokenAddress, provider);
    return token.functions.balanceOf(address);
}