viem — TypeScript инструменты для удобной разработки Web3

--- name: viem description: This skill should be used when the user asks about "viem", "viem client", "viem actions", "TypeScript Ethereum", "createPublicClient", "createWalletClient", "parseEther", "formatEther", "readContract", "writeContract", or mentions using viem for blockchain interactions. --- # Viem ## Overview Viem is a TypeScript interface for Ethereum that provides low-level stateless primitives for interacting with the blockchain. It focuses on developer experience, stability, bundle size, and performance. Key features: - Automatic type safety and inference - Tree-shakable lightweight modules - Optimized encoding/parsing - Composable APIs ## Core Concepts | Concept | Description | | -------------- | ------------------------------------------------------------- | | **Clients** | `PublicClient`, `WalletClient`, `TestClient` - entry points | | **Transports** | Connection layer (`http`, `webSocket`, `custom`) | | **Actions** | Operations like `getBlockNumber`, `sendTransaction` | | **Chains** | Chain configurations (`mainnet`, `sepolia`, `arbitrum`, etc.) | ## Constants Viem exports useful constants for common values: ```typescript import { maxUint256, maxUint128, maxInt256, zeroAddress, zeroHash } from "viem"; // Max values for uint types maxUint256; // 2n ** 256n - 1n maxUint128; // 2n ** 128n - 1n // Zero values zeroAddress; // 0x0000000000000000000000000000000000000000 zeroHash; // 0x0000000000000000000000000000000000000000000000000000000000000000 ``` ## Utilities ### Unit Conversion Convert between wei and human-readable values: ```typescript import { parseEther, formatEther, parseUnits, formatUnits } from "viem"; // ETH <-> Wei (18 decimals) parseEther("1"); // 1000000000000000000n formatEther(1000000000000000000n); // "1" // Custom decimals (e.g., USDC with 6 decimals) parseUnits("100", 6); // 100000000n formatUnits(100000000n, 6); // "100" ``` ### ABI Utilities Parse human-readable ABIs: ```typescript import { parseAbi, parseAbiItem } from "viem"; const abi = parseAbi([ "function balanceOf(address owner) view returns (uint256)", "function transfer(address to, uint256 amount) returns (bool)", "event Transfer(address indexed from, address indexed to, uint256 amount)", ]); const item = parseAbiItem("function name() view returns (string)"); ``` ### Address Utilities ```typescript import { getAddress, isAddress, isAddressEqual } from "viem"; // Checksum address getAddress("0xabc..."); // "0xAbc..." (checksummed) // Validation isAddress("0x..."); // true/false isAddressEqual("0xAbc...", "0xabc..."); // true (case-insensitive) ``` ## Clients ### Public Client (Read Operations) For querying blockchain state: ```typescript import { createPublicClient, http } from "viem"; import { mainnet } from "viem/chains"; const publicClient = createPublicClient({ chain: mainnet, transport: http(), // or http("https://eth-mainnet.g.alchemy.com/v2/...") }); // Read operations const blockNumber = await publicClient.getBlockNumber(); const balance = await publicClient.getBalance({ address: "0x..." }); const block = await publicClient.getBlock(); ``` ### Wallet Client (Write Operations) For signing and sending transactions: ```typescript import { createWalletClient, http } from "viem"; import { privateKeyToAccount } from "viem/accounts"; import { mainnet } from "viem/chains"; const account = privateKeyToAccount("0x..."); const walletClient = createWalletClient({ account, chain: mainnet, transport: http(), }); // Send transaction const hash = await walletClient.sendTransaction({ to: "0x...", value: parseEther("0.1"), }); ``` ### Browser Wallet Client For browser environments with injected wallets: ```typescript import "viem/window"; import { createWalletClient, custom } from "viem"; import { mainnet } from "viem/chains"; const walletClient = createWalletClient({ chain: mainnet, transport: custom(window.ethereum!), }); // Request accounts const [address] = await walletClient.requestAddresses(); ``` ### Extending Clients Combine capabilities using `.extend()`: ```typescript import { createWalletClient, http, publicActions } from "viem"; import { mainnet } from "viem/chains"; const client = createWalletClient({ chain: mainnet, transport: http(), }).extend(publicActions); // Now supports both wallet and public actions const balance = await client.getBalance({ address: "0x..." }); const hash = await client.sendTransaction({ to: "0x...", value: 1n }); ``` ## Contract Interactions ### Reading from Contracts ```typescript import { createPublicClient, http } from "viem"; import { mainnet } from "viem/chains"; const publicClient = createPublicClient({ chain: mainnet, transport: http(), }); const abi = [ { inputs: [{ name: "owner", type: "address" }], name: "balanceOf", outputs: [{ name: "", type: "uint256" }], stateMutability: "view", type: "function", }, ] as const; const balance = await publicClient.readContract({ address: "0x...", // Contract address abi, functionName: "balanceOf", args: ["0x..."], // Owner address }); ``` ### Writing to Contracts ```typescript const hash = await walletClient.writeContract({ address: "0x...", abi, functionName: "transfer", args: ["0x...", parseUnits("100", 18)], }); ``` ### Simulating Before Writing Simulate a transaction before sending: ```typescript const { request } = await publicClient.simulateContract({ address: "0x...", abi, functionName: "transfer", args: ["0x...", parseUnits("100", 18)], account: "0x...", }); const hash = await walletClient.writeContract(request); ``` ## Account Types ### Local Accounts For server-side or controlled environments: ```typescript import { privateKeyToAccount, mnemonicToAccount } from "viem/accounts"; // From private key const account = privateKeyToAccount("0x..."); // From mnemonic const account = mnemonicToAccount("legal winner thank year wave sausage ..."); ``` ### JSON-RPC Accounts For browser wallets: ```typescript import "viem/window"; const [account] = await window.ethereum!.request({ method: "eth_requestAccounts", }); ``` ## Chain Configuration ### Built-in Chains ```typescript import { mainnet, sepolia, arbitrum, optimism, polygon, base } from "viem/chains"; const client = createPublicClient({ chain: arbitrum, transport: http(), }); ``` ### Custom Chains ```typescript import { defineChain } from "viem"; const customChain = defineChain({ id: 123456, name: "My Chain", nativeCurrency: { name: "ETH", symbol: "ETH", decimals: 18 }, rpcUrls: { default: { http: ["https://rpc.mychain.com"] }, }, blockExplorers: { default: { name: "Explorer", url: "https://explorer.mychain.com" }, }, }); ``` ## Documentation This skill provides a reference for common operations. For comprehensive documentation, fetch the full viem docs using context7 MCP: ``` Library ID: /wevm/viem ``` Use context7 to query specific topics: - `clients` - Client types and configuration - `actions` - Available actions (read, write, wallet) - `accounts` - Local and JSON-RPC accounts - `contract` - Contract interactions (`readContract`, `writeContract`) - `abi` - ABI encoding/decoding utilities - `chains` - Supported chains and custom chain configuration ### Fetching Documentation To fetch viem documentation for a specific topic: 1. Resolve the library ID with `mcp__context7__resolve-library-id` (or use `/wevm/viem` directly) 2. Call `mcp__context7__get-library-docs` with the topic parameter Example topics: `"getting started"`, `"wallet client"`, `"send transaction"`, `"read contract"`.