typechain

What is typechain?

TypeChain is a tool for generating TypeScript typings for Ethereum smart contracts. It helps developers interact with smart contracts in a type-safe manner, reducing runtime errors and improving the development experience.

What are typechain's main functionalities?

Generating TypeScript typings for smart contracts

This command generates TypeScript typings for smart contracts using the Ethers.js target. The generated typings are placed in the 'src/types' directory, and the input JSON files are located in the 'artifacts' directory.

npx typechain --target ethers-v5 --out-dir src/types './artifacts/**/*.json'

Using generated typings in a TypeScript project

This code demonstrates how to use the generated TypeScript typings in a TypeScript project. It imports the typings for a contract named 'MyContract', interacts with the contract using Ethers.js, and logs the result of calling a method on the contract.

import { MyContract } from './types/MyContract';

async function main() {
  const myContract: MyContract = await ethers.getContractAt('MyContract', '0x123...');
  const value = await myContract.myMethod();
  console.log(value);
}

Other packages similar to typechain

ethers

Ethers.js is a library for interacting with the Ethereum blockchain and its ecosystem. While it does not generate TypeScript typings for smart contracts, it provides a comprehensive set of tools for interacting with Ethereum, including contract interaction, wallet management, and more. TypeChain can generate typings specifically for use with Ethers.js.

web3

Web3.js is a collection of libraries that allow you to interact with a local or remote Ethereum node using HTTP, IPC, or WebSocket. Similar to Ethers.js, it does not generate TypeScript typings for smart contracts but provides a wide range of functionalities for interacting with the Ethereum blockchain. TypeChain can also generate typings for use with Web3.js.

truffle

Truffle is a development environment, testing framework, and asset pipeline for Ethereum. It provides a suite of tools for developing smart contracts, including compilation, deployment, and testing. While Truffle does not generate TypeScript typings, it can be used in conjunction with TypeChain to provide a complete development workflow.

README

Typechain

🔌 Typescript bindings for Ethereum smartcontracts

Installation

npm install --save-dev typechain

yarn add --dev typechain

Note: Typechain requires web3 in version: 0.20.x.

Usage

typechain [--force] [glob]

• glob - pattern that will be used to find ABIs, remember about adding quotes: typechain "**/*.json"
• --force - force overwrite existing files

Features ⚡

• static typing - you will never call not existing method again
• IDE support - works with any IDE supporting Typescript
• revamped API - native promises, safety checks and more!
• compatibility - under the hood it uses web3 so it's 100% compatible

Demo 🏎️

fullsize

Example repo

Getting started 📚

Motivation

Interacting with blockchain in Javascript is a pain. Web3 interface is sluggish and when you want to use from Typescript it gets even worse. Often, you can't be sure what given method call will actually do without looking at ABI file. Typechain is here to solve these problems (as long as you use Typescript).

How does it work?

Typechain is code generator - provide ABI file and you will get Typescript class with flexible interface for interacting with blockchain.

In future we plan to leverage something like tsc plugin system to come up with much more elegant solution. You can keep track of Allow "Compiler Plugins" issue.

Step by step guide

Install typechain with yarn add --dev typechain.

Run typechain (you might need to make sure that it's available in your path if you installed it only locally), it will automatically find all .abi files in your project and generate Typescript classes based on them. You can specify your glob pattern: typechain "**/*.abi.json". node_modules are always ignored. Use --force to overwrite already existing files. We recommend git ignoring these generated files and making typechain part of your build process.

That's it! Now, just import contract bindings as any other file import { MyAwesomeContract } from './contracts/MyAwesomeContract' and start interacting with it. We use named exports because of this.

API

Let's take a look at typings generated for simple smartcontract:

import { BigNumber } from "bignumber.js";
import {
  TypechainContract,
  promisify,
  ITxParams,
  IPayableTxParams,
  DeferredTransactionWrapper
} from "./typechain-runtime";

export class DumbContract extends TypechainContract {
  public readonly rawWeb3Contract: any;

  public constructor(web3: any, address: string) {
    const abi = [
      // ... ABI
    ];
    super(web3, address, abi);
  }

  static async createAndValidate(web3: any, address: string): Promise<DumbContract> {
    const contract = new DumbContract(web3, address);
    const code = await promisify(web3.eth.getCode, [address]);
    if (code === "0x0") {
      throw new Error(`Contract at ${address} doesn't exist!`);
    }
    return contract;
  }

  public get counter(): Promise<BigNumber> {
    return promisify(this.rawWeb3Contract.counter, []);
  }
  public get SOME_VALUE(): Promise<boolean> {
    return promisify(this.rawWeb3Contract.SOME_VALUE, []);
  }
  public counterArray(index: BigNumber | number): Promise<BigNumber> {
    return promisify(this.rawWeb3Contract.counterArray, [index]);
  }
  public returnAll(): Promise<[BigNumber, BigNumber]> {
    return promisify(this.rawWeb3Contract.returnAll, []);
  }
  public counterWithOffset(offset: BigNumber | number): Promise<BigNumber> {
    return promisify(this.rawWeb3Contract.counterWithOffset, [offset]);
  }

  public countupForEtherTx(): DeferredTransactionWrapper<IPayableTxParams> {
    return new DeferredTransactionWrapper<IPayableTxParams>(this, "countupForEther", []);
  }
  public countupTx(offset: BigNumber | number): DeferredTransactionWrapper<ITxParams> {
    return new DeferredTransactionWrapper<ITxParams>(this, "countup", [offset]);
  }
}

Using it can be as simple as:

const dumbContract = await DumbContract.createAndValidate(web3, contractAddress);

console.log(`Current counter value is: ${await dumbContract.counter}`);

console.log("Lets increase it by 2... This results in state change so we need to create tx.");
await dumbContract.countupTx(2).send({ from: accounts[0], gas: GAS_LIMIT_STANDARD });

console.log(`Current counter value is: ${await dumbContract.counter}`);

console.log("We can also get signed tx data: ");
console.log(await dumbContract.countupTx(2).getData());

console.log("When calling payable txs, Typechain will make sure that you provide ether value:");
await dumbContract
  .countupForEtherTx()
  .send({ from: accounts[0], gas: GAS_LIMIT_STANDARD, value: 10 });
console.log(`Current counter value is: ${await dumbContract.counter}`);

which gives following output:

Current counter value is: 0
Lets increase it by 2... This results in state change so we need to create tx.
Current counter value is: 2
We can also get signed tx data:
0x7916df080000000000000000000000000000000000000000000000000000000000000002
When calling payable txs, Typechain will make sure that you provide ether value:
Current counter value is: 12

FAQ 🤔

Q: Should I commit generated files to my repository?

A: NO — we believe that no generated files should go to git repository. You should git ignore them and make typechain run automatically for example in post install hook in package.json:

"postinstall":"typechain"

When you update ABI, just regenerate files with Typechain and Typescript compiler will find any breaking changes for you.

Q: How do I customize generated classes?

A: You can create your own class that extends generated one and adds additional methods etc.

Currently we discuss various ideas around extendibility including APIs files (adding semantics to ABIs for covering popular cases like working with dates) or using user-defined templates for generated code.

Roadmap 🛣️

• improve generated code (auto formatting, more checks, wiring contracts together)
• events

Running tests

You need to have solc ^0.4.4 installed on your system. Then just do yarn test.

Debugging 🐞

DEBUG=typechain typechain