Viem极简教程：与链上合约交互
- Carry
- 更新于 5天前
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Viem是一个相当新的web3库，它专注于EVM，提供了更好的开发体验，更小的包体积等等。在本文中，将使用foundry部署一个简单的合约，并在node环境下使用viem与部署的链上合约执行读写交互。
Viem是一个相当新的web3库，它专注于EVM，提供了更好的开发体验，更小的包体积等等。在本文中，将使用foundry部署一个简单的合约，并在node环境下使用viem与部署的链上合约执行读写交互。
- Viem docs — https://viem.sh/docs/getting-started.html
- GitHub repository for the code used in this article — https://github.com/CarryWang/viem-playground
使用foundry创建合约
首先使用foundry来部署一个简单的合约。首先新建一个foundry项目，使用forge init命令。
forge init viem-foundry创建好后的项目结构会像下面这样。
➜ viem-foundry git:(main) ✗ tree . -L 1 . ├── README.md ├── foundry.toml ├── lib ├── script ├── src └── testfoundry会在
src中创建一个叫Counter.sol的示例合约。对这个合约稍作修改，增加一个decrement方法。// SPDX-License-Identifier: UNLICENSED pragma solidity ^0.8.13;
contract Counter { uint256 public number;
function setNumber(uint256 newNumber) public { number = newNumber; }
function increment() public { number++; }
function decrement() public { number--; } }
同时在`test/Counter.t.sol`中增加一个`test_Decrement`的测试用例。
```solidity
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;
import {Test, console} from "forge-std/Test.sol";
import {Counter} from "../src/Counter.sol";
contract CounterTest is Test {
Counter public counter;
function setUp() public {
counter = new Counter();
counter.setNumber(0);
}
function test_Increment() public {
counter.increment();
assertEq(counter.number(), 1);
}
function test_Decrement() public {
counter.setNumber(1);
counter.decrement();
assertEq(counter.number(), 0);
}
function testFuzz_SetNumber(uint256 x) public {
counter.setNumber(x);
assertEq(counter.number(), x);
}
}
接下来执行forge build命令。
$ forge build
Compiling 27 files with Solc 0.8.19
Solc 0.8.19 finished in 1.27s
Compiler run successful!接着执行forge test命令。终端会显示下面的结果，所有的用例都PASS都没有问题，就可以部署合约了。
viem-foundry git:(main) forge test
[⠢] Compiling...
No files changed, compilation skipped
Ran 3 tests for test/Counter.t.sol:CounterTest
[PASS] testFuzz_SetNumber(uint256) (runs: 256, μ: 31098, ~: 31332)
[PASS] test_Decrement() (gas: 21546)
[PASS] test_Increment() (gas: 31359)
Suite result: ok. 3 passed; 0 failed; 0 skipped; finished in 12.49ms (8.09ms CPU time)
Ran 1 test suite in 250.79ms (12.49ms CPU time): 3 tests passed, 0 failed, 0 skipped (3 total tests)
这里使用sepolia作为测试部署。使用forge create命令。这里的--rpc-url填入sepolia的rpc，可以使用公共的rpc节点，--private-key就是你的钱包私钥，--etherscan-api-key用于验证合约用，这个api-key可以去https://etherscan.io/login注册账号获得。
forge create --rpc-url <your_rpc_url> \
--private-key <your_private_key> \
--etherscan-api-key <your_etherscan_api_key> \
--verify \
src/Counter.sol:Counter部署完成后，就可以在sepolia的区块链浏览器中查看到部署好的合约，这里已经部署好的合约可以在这里查看。
经过验证后的合约，在Contract标签栏上会有一个绿色的小勾，并且可以查看合约的源码。
在区块链浏览器中可以直接与合约进行交互，在Write Contract中可以看到合约中的函数，可以通过链接钱包，进行对合约的写入操作。当然，执行每一个操作都需要支付gas费。
在Read Contract中可以查看所有的public变量。
至此，合约的部署工作已经全部完成了。
使用Viem与合约交互
接下来是viem的部分，这一部分主要是关于如何使用viem与合约进行交互。
首先，创建一个viem-scripts文件夹，首先使用pnpm初始化项目，使用pnpm init，终端会出现以下信息。
{
"name": "viem-scripts",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"keywords": [],
"author": "",
"license": "ISC"
}
接下来需要安装一些必要的依赖，使用pnpm安装。
pnpm install dotenv viem
pnpm install -D typescript ts-node @types/node安装依赖后，需要在项目中初始化typescript的配置文件，输入以下命令。
npx tsc --init项目根目录下会自动创建一个tsconfig.json文件，终端显示如下。
Created a new tsconfig.json with:
TS
target: es2016
module: commonjs
strict: true
esModuleInterop: true
skipLibCheck: true
forceConsistentCasingInFileNames: true
You can learn more at https://aka.ms/tsconfig新建一个index.ts文件，创建一个client，调用viem提供的createPublicClient函数，该函数需要传入一个对象，对象包含两个重要的字段chain和transport。
import { createPublicClient, http } from "viem";
import { sepolia } from "viem/chains";
const client = createPublicClient({
chain: sepolia,
transport: http(),
});本文的合约部署在sepolia上，所以这里的chain使用sepolia，viem/chains中提供了很多公链，更多支持的链可以这个列表。transport指的是前端与合约的通信方式，viem中的transport支持三种模式，分别是 HTTP Transport，WebSocket Transport 和 Custom Transport ，这里使用最常用的http方式。
有了client，就可以与链做交互了，先做一个最简单的交互，查询当前链的区块高度。输入下面的代码。
async function main() {
const blockNumber = await client.getBlockNumber();
console.log(blockNumber);
}
main();打开根目录中的package.json，在scripts中添加"start": "ts-node index.ts"。
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"start": "ts-node index.ts"
},运行pnpm start，终端会显示目前的区块高度。注意，你运行的时候，这个值会和我的不一样，因为区块数一直在增加。
> viem-scripts@1.0.0 start /viem-playground/viem-scripts
> ts-node index.ts
6153864n为了和合约交互，需要知道合约的abi。在foundry项目中，当我们执行forge build后，会把所有项目中涉及到的所有合约进行编译，并在根目录下会生成一个out文件夹，文件夹内会对应生成每个合约的json文件。
.
├── cache
├── lib
├── out
│ ├── Base.sol
│ │ ├── CommonBase.json
│ │ ├── ScriptBase.json
│ │ └── TestBase.json
│ ├── Counter.s.sol
│ │ └── CounterScript.json
│ ├── Counter.sol
│ │ └── Counter.json
│ ├── Counter.t.sol
│ │ └── CounterTest.json
│ ├── IERC165.sol
│ │ └── IERC165.json
│ ├── IERC20.sol
│ │ └── IERC20.json
│ ├── IERC721.sol
│ │ ├── IERC721.json
│ │ ├── IERC721Enumerable.json
│ │ ├── IERC721Metadata.json
│ │ └── IERC721TokenReceiver.json
│ ├── IMulticall3.sol
│ │ └── IMulticall3.json
│ ├── MockERC20.sol
│ │ └── MockERC20.json
│ ├── MockERC721.sol
│ │ ├── IERC721TokenReceiver.json
│ │ └── MockERC721.json
│ ├── Script.sol
│ │ └── Script.json
│ ├── StdAssertions.sol
│ │ └── StdAssertions.json
│ ├── StdChains.sol
│ │ └── StdChains.json
│ ├── StdCheats.sol
│ │ ├── StdCheats.json
│ │ └── StdCheatsSafe.json
│ ├── StdError.sol
│ │ └── stdError.json
│ ├── StdInvariant.sol
│ │ └── StdInvariant.json
│ ├── StdJson.sol
│ │ └── stdJson.json
│ ├── StdMath.sol
│ │ └── stdMath.json
│ ├── StdStorage.sol
│ │ ├── stdStorage.json
│ │ └── stdStorageSafe.json
│ ├── StdStyle.sol
│ │ └── StdStyle.json
│ ├── StdToml.sol
│ │ └── stdToml.json
│ ├── StdUtils.sol
│ │ └── StdUtils.json
│ ├── Test.sol
│ │ └── Test.json
│ ├── Vm.sol
│ │ ├── Vm.json
│ │ └── VmSafe.json
│ ├── console.sol
│ │ └── console.json
│ ├── console2.sol
│ │ └── console2.json
│ └── safeconsole.sol
│ └── safeconsole.json
├── script
├── src
└── test找到Counter.json文件，可以看到里面包含了几个主要字段，abi，bytecode，deployedBytecode，methodIdentifiers，rawMetadata，metadata以及id。这些字段构成了描述一个合约的完整信息。
{
"abi": [
{
"type": "function",
"name": "decrement",
"inputs": [],
"outputs": [],
"stateMutability": "nonpayable"
},
{
"type": "function",
"name": "increment",
"inputs": [],
"outputs": [],
"stateMutability": "nonpayable"
},
{
"type": "function",
"name": "number",
"inputs": [],
"outputs": [{ "name": "", "type": "uint256", "internalType": "uint256" }],
"stateMutability": "view"
},
{
"type": "function",
"name": "setNumber",
"inputs": [
{ "name": "newNumber", "type": "uint256", "internalType": "uint256" }
],
"outputs": [],
"stateMutability": "nonpayable"
}
],
"bytecode": {
"object": "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",
"sourceMap": "65:251:25:-:0;;;;;;;;;;;;;;;;;;;",
"linkReferences": {}
},
"deployedBytecode": {
"object": "0x6080604052348015600f57600080fd5b506004361060465760003560e01c80632baeceb714604b5780633fb5c1cb1460535780638381f58a146063578063d09de08a14607d575b600080fd5b60516083565b005b6051605e36600460a4565b600055565b606b60005481565b60405190815260200160405180910390f35b60516097565b60008054908060908360d2565b9190505550565b60008054908060908360e6565b60006020828403121560b557600080fd5b5035919050565b634e487b7160e01b600052601160045260246000fd5b60008160de5760de60bc565b506000190190565b60006001820160f55760f560bc565b506001019056fea2646970667358221220aa623ffc9dd48bbbf1da02199cadc16e0e718c5d6cc383341f77e57e2cb4412564736f6c63430008190033",
"sourceMap": "65:251:25:-:0;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;261:53;;;:::i;:::-;;116:80;;;;;;:::i;:::-;171:6;:18;116:80;88:21;;;;;;;;;345:25:27;;;333:2;318:18;88:21:25;;;;;;;202:53;;;:::i;261:::-;299:6;:8;;;:6;:8;;;:::i;:::-;;;;;;261:53::o;202:::-;240:6;:8;;;:6;:8;;;:::i;14:180:27:-;73:6;126:2;114:9;105:7;101:23;97:32;94:52;;;142:1;139;132:12;94:52;-1:-1:-1;165:23:27;;14:180;-1:-1:-1;14:180:27:o;381:127::-;442:10;437:3;433:20;430:1;423:31;473:4;470:1;463:15;497:4;494:1;487:15;513:136;552:3;580:5;570:39;;589:18;;:::i;:::-;-1:-1:-1;;;625:18:27;;513:136::o;654:135::-;693:3;714:17;;;711:43;;734:18;;:::i;:::-;-1:-1:-1;781:1:27;770:13;;654:135::o",
"linkReferences": {}
},
"methodIdentifiers": {
"decrement()": "2baeceb7",
"increment()": "d09de08a",
"number()": "8381f58a",
"setNumber(uint256)": "3fb5c1cb"
},
"rawMetadata": "{\"compiler\":{\"version\":\"0.8.25+commit.b61c2a91\"},\"language\":\"Solidity\",\"output\":{\"abi\":[{\"inputs\":[],\"name\":\"decrement\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"increment\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"number\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"newNumber\",\"type\":\"uint256\"}],\"name\":\"setNumber\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"}],\"devdoc\":{\"kind\":\"dev\",\"methods\":{},\"version\":1},\"userdoc\":{\"kind\":\"user\",\"methods\":{},\"version\":1}},\"settings\":{\"compilationTarget\":{\"src/Counter.sol\":\"Counter\"},\"evmVersion\":\"paris\",\"libraries\":{},\"metadata\":{\"bytecodeHash\":\"ipfs\"},\"optimizer\":{\"enabled\":true,\"runs\":200},\"remappings\":[\":forge-std/=lib/forge-std/src/\"]},\"sources\":{\"src/Counter.sol\":{\"keccak256\":\"0xf45df1ccab4c7ce7c7c8b529079d4e3c914cf09350e26d1b2a168e89792c9124\",\"license\":\"UNLICENSED\",\"urls\":[\"bzz-raw://7f911aefa13cda2bf5eadfb5cc672af7dceee749563afb27e237f225a221cb4a\",\"dweb:/ipfs/QmdUkxZJkFgz8oC9ARaKhRJNVRGvyGnC8TFNCvh7ejc5k2\"]}},\"version\":1}",
"metadata": {
"compiler": { "version": "0.8.25+commit.b61c2a91" },
"language": "Solidity",
"output": {
"abi": [
{
"inputs": [],
"stateMutability": "nonpayable",
"type": "function",
"name": "decrement"
},
{
"inputs": [],
"stateMutability": "nonpayable",
"type": "function",
"name": "increment"
},
{
"inputs": [],
"stateMutability": "view",
"type": "function",
"name": "number",
"outputs": [
{ "internalType": "uint256", "name": "", "type": "uint256" }
]
},
{
"inputs": [
{
"internalType": "uint256",
"name": "newNumber",
"type": "uint256"
}
],
"stateMutability": "nonpayable",
"type": "function",
"name": "setNumber"
}
],
"devdoc": { "kind": "dev", "methods": {}, "version": 1 },
"userdoc": { "kind": "user", "methods": {}, "version": 1 }
},
"settings": {
"remappings": ["forge-std/=lib/forge-std/src/"],
"optimizer": { "enabled": true, "runs": 200 },
"metadata": { "bytecodeHash": "ipfs" },
"compilationTarget": { "src/Counter.sol": "Counter" },
"evmVersion": "paris",
"libraries": {}
},
"sources": {
"src/Counter.sol": {
"keccak256": "0xf45df1ccab4c7ce7c7c8b529079d4e3c914cf09350e26d1b2a168e89792c9124",
"urls": [
"bzz-raw://7f911aefa13cda2bf5eadfb5cc672af7dceee749563afb27e237f225a221cb4a",
"dweb:/ipfs/QmdUkxZJkFgz8oC9ARaKhRJNVRGvyGnC8TFNCvh7ejc5k2"
],
"license": "UNLICENSED"
}
},
"version": 1
},
"id": 25
}
使用viem与合约交互需要用到abi以及bytecode。
在viem-scripts项目文件夹中，新建一个abi.ts文件，声明并暴露两个变量abi和address。abi这个变量的内容来自Counter.json,address就是sepolia上部署的Counter合约地址。注意，下面代码中第30行，需要添加as const关键词，这样viem可以智能的读取里面的function信息。
export const abi = [
{
type: "function",
name: "decrement",
inputs: [],
outputs: [],
stateMutability: "nonpayable",
},
{
type: "function",
name: "increment",
inputs: [],
outputs: [],
stateMutability: "nonpayable",
},
{
type: "function",
name: "number",
inputs: [],
outputs: [{ name: "", type: "uint256", internalType: "uint256" }],
stateMutability: "view",
},
{
type: "function",
name: "setNumber",
inputs: [{ name: "newNumber", type: "uint256", internalType: "uint256" }],
outputs: [],
stateMutability: "nonpayable",
},
] as const;
export const address = "0x6b565dE192A1Be17a4F077B5Fda6b3A100498790" as const;
接下来需要导入私钥，在项目根文件夹下新建.env文件，添加私钥。下面的私钥是示例，假数据。注意，私钥很重要，不要轻易外泄。
PRIVATE_KEY=45210d79205254d4505912eb32371f7f2f0b059ed771898554f0d0f169c87e45同时，记得将.env文件添加到.gitignore文件中，确保不要将此文件上传至github或其他代码托管平台上。
.env
node_modules/在index.ts中配置dotenv，导入.env中的私钥变量。调用privateKeyToAccount函数，传入私钥。
import { createPublicClient, http } from "viem";
import { sepolia } from "viem/chains";
import { privateKeyToAccount } from "viem/accounts";
import dotenv from "dotenv";
dotenv.config();
const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);
使用本地私钥的方式与合约做交互需要使用viem的Wallet Client。导入createWalletClient方法，并创建一个walletClient。注意，http方法接受自定义rpc节点链接，如果你有自己的rpc可以传入其中，否则viem将会使用公共节点，有时候公共节点会比较不稳定，同时也有速度限制。
import { createPublicClient, createWalletClient, http } from "viem";
import { sepolia } from "viem/chains";
import { privateKeyToAccount } from "viem/accounts";
import dotenv from "dotenv";
dotenv.config();
const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);
const rpc = process.env.ETH_RPC_URL;
const walletClient = createWalletClient({
account,
chain: sepolia,
transport: http(rpc),
});接下来实现与合约交互，首先实现读合约的操作。导入abi和address，使用readContract方法，传入address，abi和functionName。注意，读取操作使用的client是Public Client而不是Wallet Client。
import { abi, address } from "./abi";
async function main() {
// const blockNumber = await client.getBlockNumber();
// console.log(blockNumber);
const number = await client.readContract({
address,
abi,
functionName: "number",
});
console.log(number);
}
main();完整的代码如下。
import { createPublicClient, createWalletClient, http } from "viem";
import { sepolia } from "viem/chains";
import { privateKeyToAccount } from "viem/accounts";
import { abi, address } from "./abi";
import dotenv from "dotenv";
dotenv.config();
const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);
const rpc = process.env.ETH_RPC_URL;
const walletClient = createWalletClient({
account,
chain: sepolia,
transport: http(rpc),
});
const client = createPublicClient({
chain: sepolia,
transport: http(rpc),
});
async function main() {
// const blockNumber = await client.getBlockNumber();
// console.log(blockNumber);
const number = await client.readContract({
address,
abi,
functionName: "number",
});
console.log(number);
}
main();
运行main函数。会得到下面的结果。可以看到输出了101。证明已经成功的从链上读取了函数的返回值。
> viem-scripts@1.0.0 start /viem-playground/viem-scripts
> ts-node index.ts
101n执行写操作就需要使用Wallet Client。改造一下main函数。首先，把获取number的函数单独抽取出来。调用walletClient的writeContract方法，注意args，这个字段接收一个数组，里面就是调用合约函数时需要传入的参数，传入number型变量时需要先转化为BigInt类型。
调用writeContract函数后会返回一个哈希值，这个哈希值可以作为waitForTransactionReceipt的参数。当对合约进行写操作时，可以看作是进行了一笔Transaction，对于以太坊来说，会在单位时间内打包多笔交易并生成一个新的区块。执行waitForTransactionReceipt会返回一个receipt对象，可以获取这次交易的信息。
async function main() {
// const blockNumber = await client.getBlockNumber();
// console.log(blockNumber);
getNumber();
const hash = await walletClient.writeContract({
address,
abi,
functionName: "setNumber",
args: [BigInt(100)],
});
console.log("The hash is:", hash);
const receipt = await client.waitForTransactionReceipt({ hash });
console.log("receipt info:", receipt);
receipt && getNumber();
}
async function getNumber() {
const number = await client.readContract({
address,
abi,
functionName: "number",
});
console.log("The number is:", number);
}
main();执行main函数，可以依次看到如下信息。可以看到number从101变成了100。
> viem-scripts@1.0.0 start /web3/viem-playground/viem-scripts
> ts-node index.ts
The number is: 101n
The hash is: 0x96c55da3ef7b9b0ef209d7329cd74a4fb1b1c493d8efad55814a156d867f96a6
receipt info: {
type: 'eip1559',
from: '0xa0466a82b961e85077d4a8debc35fbf6cf18d464',
to: '0x6b565de192a1be17a4f077b5fda6b3a100498790',
status: 'success',
cumulativeGasUsed: 20730581n,
logsBloom: '0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000',
logs: [],
transactionHash: '0x96c55da3ef7b9b0ef209d7329cd74a4fb1b1c493d8efad55814a156d867f96a6',
contractAddress: null,
gasUsed: 26416n,
blockHash: '0xce27361d3088232abd4f63fc3f5aaf9c63c7bd38f3f54f3df08dbe26f8fe6147',
blockNumber: 6167597n,
transactionIndex: 136,
effectiveGasPrice: 1964520099n
}
The number is: 100n去sepolia的区块链浏览器中也能看到每一次调用成功后的Transaction Hash。
同样，在区块链浏览器中查询也能看到number更新了。
至此，使用viem与合约的交互工作已经完成。viem的更多功能请参考官方文档。
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