EVM Transactions

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简介

• 当用户需要从 EVM 链（例如 Ethereum mainnet、Arbitrum、Optimism 等）进行转账或兑换时，Skip Go API 会返回一个 EvmTx 类型，供开发者交给用户签名。
• 与 CosmosSDK 交易不同，EVM 交易没有消息（message）的概念，因此这个对象与“消息”并不是一一对应的；对 Cosmos 开发者来说，“消息”可能是更熟悉的概念。
• 本文面向尚不熟悉 EVM 中交易构造概念、但需要使用 EvmTx 帮助用户在 EVM 链之间转入或转出的 CosmosSDK 开发者。

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EvmTx 数据结构

• to：该交易交互的智能合约或外部拥有账户（EOA）地址，格式为带 0x 前缀的十六进制字符串（例如 0xfc05aD74C6FE2e7046E091D6Ad4F660D2A159762）
• value：该交易发送给其所交互合约的 wei 数量（1 ETH = 1^18 WEI）
• data：该交易用于调用所交互智能合约的 calldata，格式为十六进制字符串。数据字节会按照被调用合约的应用二进制接口（ABI）进行解析。如果该字段为空，表示这笔交易是在向某个地址转账，而不是调用合约。
• required_erc20_approvals：必须授予特定智能合约的权限，使其能够代表最终用户花费或转移一定数量的 ERC-20 代币。这使智能合约能够执行更复杂的流程，其中可能涉及转移用户的一部分 ERC-20 代币。
  • 如果路由需要任何 ERC-20 授权，Skip Go 总会返回该字段。客户端有责任检查用户当前授权额度是否已经达到或超过返回所需的授权额度（例如，集成方允许最大授权的情况）。如果该字段非空且用户没有所需授权，则必须先完成授权、签名并提交，然后才能将响应中由其他字段填充的 EvmTx 提交到网络。否则，执行时会因权限错误而失败。
  • Skip 的 ERC20Approval 对象有 3 个定义授权的字段：
    • token_contract：被授予授权的 ERC-20 代币合约地址
    • spender：将被授予支出权限的合约地址
    • amount：授权 spender 可支出的 token_contract 代币数量
  • 关于 ERC-20 授权的更多信息，请参阅 EIP-2612。
• chain_id：这一点与 Cosmos 场景中的含义相同（只是链的标识符），但它是 int 而不是字符串。

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构造并签名 EVM 交易示例

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1. 安装签名库和 Skip 库

• viem
• ethers.js
• web3.js

npm i viem
npm i @skip-go/client

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1. 使用 EVM WalletClient 对象初始化 SkipClient 客户端

• 在底层使用 RPC provider 查询链上构造交易所需的数据（例如 nonce、gas price 等）
• 暴露可用于构造、签名和广播交易的 API

import { createWalletClient, custom} from 'viem';
import * as chains from 'viem/chains';
import { SkipClient } from '@skip-go/client';

const
const skipClient = new SkipClient({
  getEVMSigner: async (chainID) => {
    const chain = extractChain({
  		chains: Object.values(chains),
  		id: parseInt(chainID)
    });
    const evmWalletClient = createWalletClient({
  		chain: chain,
  		transport: custom(window.ethereum!)
  	});
    return evmWalletClient;
  }
});

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2. 使用 SkipClient 请求路由并获取所需链

const route = await skipClient.route({
  amountIn: "1000",
  sourceAssetDenom: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
  sourceAssetChainID: "1",
  destAssetDenom: "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
  destAssetChainID: "42161",
  smartRelay: true,
  smartSwapOptions: {
    splitRoutes: true
  }
};

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3. 获取所有所需链的用户地址

let userAddresses = []
const requiredAddresses = route.requiredChainAddresses;
// iterate over chain IDs for chains that require addresses
for (const chainID of requiredAddresses) {
  	// Check that the chain is an EVM chain
    if (parseInt(chainID)) {
      // use signer library to get address from wallet
      const chain = extractChain({
        chains: Object.values(chains),
        id: parseInt(chainID)
      });
      const evmWalletClient = createWalletClient({
        chain: chain,
        transport: custom(window.ethereum!)
      });
      const [address] = await client.requestAddresses();
      // add to map
      userAddresses.append({address: address, chainID: chainID})
    } else {
      // handle cosmos and SVM wallets -- not shown
    }

});
return evmWalletClient;
}

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4. 使用 SkipClient 执行路由

await skipClient.executeRoute({
  route:route,
  userAddresses: userAddresses
});

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Intro

• When a user needs to transfer or swap from an EVM chain (e.g. Ethereum mainnet, Arbitrum, Optimism, etc…), the Skip Go API will return an EvmTx type for the developer to pass to the user for signing
• Unlike CosmosSDK transactions, EVM transactions do not have a notion of messages, so this object doesn’t correspond 1-to-1 to a “message”, which might be a more familiar notion to Cosmos developers
• This doc is intended for CosmosSDK developers who aren’t already familiar with the concepts of transaction construction in the EVM and need to use EvmTx to help their users move from/to EVM chains.

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EvmTx Data Structure

• to: The address of the smart contract or externally owned account (EOA) with which this transaction interacts, as a hex-string prefixed with 0x (e.g. 0xfc05aD74C6FE2e7046E091D6Ad4F660D2A159762)
• value: The amount of wei this transaction sends to the contract its interacting with (1 ETH = 1^18 WEI)
• data: The calldata this transaction uses to call the smart contract it interacts with, as a hex string. The data bytes will be interpreted according to the application-binary-interface (ABI) of the contract that’s being interacted with. If this field is empty, it means the transaction is sending funds to an address, rather than calling a contract.
• required_erc20_approvals: The permissions that must be granted to a specific smart contract to spend or transfer a certain amount of their ERC-20 tokens on behalf of the end user. This allows smart contracts to execute expressive flows that may involve moving some amount of the user’s ERC-20 tokens
  • Skip Go will always return this field if there are any erc20 approvals needed for the route. It is the client’s responsibility to check if the user’s approval is already at or above the returned approval needed (for example, if the integrator allows for max approvals). If this field is non-empty and the user does not have the approvals necessary, the approval must be granted, signed, and submitted before the EvmTx populated by the other fields in the response can be submitted to the network. Otherwise, it will fail to execute with a permission error.
  • Skip’s ERC20Approval object has 3 fields that define approval: _ token_contract: The address of the ERC-20 token on which the approval is granted _ spender: The address of the contract to which the approval will grant spend authority * amount: The amount of token_contract tokens the approval will grant the spender to spend
  • Check out EIP-2612 for more information on ERC-20 approvals.
• chain_id: This is the same as in the Cosmos context (simply an identifier for the chain), but it’s an int instead of a string

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Example constructing & signing an EVM Transaction

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1. Install Signing Library and Skip Library

• viem
• ethers.js
• web3.js

npm i viem
npm i @skip-go/client

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1. Initialize the SkipClient client with the EVM WalletClient object

• Use an RPC provider under the hood to query the chain for necessary data to create transactions (e.g. nonce, gas price, etc…)
• Expose an API that allows constructing, signing, and broadcasting transactions

import { createWalletClient, custom} from 'viem';
import * as chains from 'viem/chains';
import { SkipClient } from '@skip-go/client';

const
const skipClient = new SkipClient({
  getEVMSigner: async (chainID) => {
    const chain = extractChain({
  		chains: Object.values(chains),
  		id: parseInt(chainID)
    });
    const evmWalletClient = createWalletClient({
  		chain: chain,
  		transport: custom(window.ethereum!)
  	});
    return evmWalletClient;
  }
});

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2. Request Route using SkipClient and get required chain

const route = await skipClient.route({
  amountIn: "1000",
  sourceAssetDenom: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
  sourceAssetChainID: "1",
  destAssetDenom: "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
  destAssetChainID: "42161",
  smartRelay: true,
  smartSwapOptions: {
    splitRoutes: true
  }
};

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3. Get User Addresses for all Required Chains

let userAddresses = []
const requiredAddresses = route.requiredChainAddresses;
// iterate over chain IDs for chains that require addresses
for (const chainID of requiredAddresses) {
  	// Check that the chain is an EVM chain
    if (parseInt(chainID)) {
      // use signer library to get address from wallet
      const chain = extractChain({
        chains: Object.values(chains),
        id: parseInt(chainID)
      });
      const evmWalletClient = createWalletClient({
        chain: chain,
        transport: custom(window.ethereum!)
      });
      const [address] = await client.requestAddresses();
      // add to map
      userAddresses.append({address: address, chainID: chainID})
    } else {
      // handle cosmos and SVM wallets -- not shown
    }

});
return evmWalletClient;
}

​

4. Execute the Route using SkipClient

await skipClient.executeRoute({
  route:route,
  userAddresses: userAddresses
});