概述: 用Go来查询ERC20代币智能合约的教程。

查询ERC20代币智能合约

首先创建一个ERC20智能合约interface。 这只是与您可以调用的函数的函数定义的契约。

  1. pragma solidity ^0.4.24;
  3. contract ERC20 {
  4.     string public constant name = "";
  5.     string public constant symbol = "";
  6.     uint8 public constant decimals = 0;
  8.     function totalSupply() public constant returns (uint);
  9.     function balanceOf(address tokenOwner) public constant returns (uint balance);
  10.     function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
  11.     function transfer(address to, uint tokens) public returns (bool success);
  12.     function approve(address spender, uint tokens) public returns (bool success);
  13.     function transferFrom(address from, address to, uint tokens) public returns (bool success);
  15.     event Transfer(address indexed from, address indexed to, uint tokens);
  16.     event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
  17. }

然后将interface智能合约编译为JSON ABI，并使用abigen从ABI创建Go包。

  1. solc --abi erc20.sol
  2. abigen --abi=erc20_sol_ERC20.abi --pkg=token --out=erc20.go

假设我们已经像往常一样设置了以太坊客户端，我们现在可以将新的token包导入我们的应用程序并实例化它。这个例子里我们用Golem 代币的地址.

  1. tokenAddress := common.HexToAddress("0xa74476443119A942dE498590Fe1f2454d7D4aC0d")
  2. instance, err := token.NewToken(tokenAddress, client)
  3. if err != nil {
  4.   log.Fatal(err)
  5. }

我们现在可以调用任何ERC20的方法。 例如，我们可以查询用户的代币余额。

  1. address := common.HexToAddress("0x0536806df512d6cdde913cf95c9886f65b1d3462")
  2. bal, err := instance.BalanceOf(&bind.CallOpts{}, address)
  3. if err != nil {
  4.   log.Fatal(err)
  5. }
  7. fmt.Printf("wei: %s\n", bal) // "wei: 74605500647408739782407023"

我们还可以读ERC20智能合约的公共变量。

  1. name, err := instance.Name(&bind.CallOpts{})
  2. if err != nil {
  3.   log.Fatal(err)
  4. }
  6. symbol, err := instance.Symbol(&bind.CallOpts{})
  7. if err != nil {
  8.   log.Fatal(err)
  9. }
  11. decimals, err := instance.Decimals(&bind.CallOpts{})
  12. if err != nil {
  13.   log.Fatal(err)
  14. }
  16. fmt.Printf("name: %s\n", name)         // "name: Golem Network"
  17. fmt.Printf("symbol: %s\n", symbol)     // "symbol: GNT"
  18. fmt.Printf("decimals: %v\n", decimals) // "decimals: 18"

我们可以做一些简单的数学运算将余额转换为可读的十进制格式。

  1. fbal := new(big.Float)
  2. fbal.SetString(bal.String())
  3. value := new(big.Float).Quo(fbal, big.NewFloat(math.Pow10(int(decimals))))
  5. fmt.Printf("balance: %f", value) // "balance: 74605500.647409"

同样的信息也可以在etherscan上查询: https://etherscan.io/token/0xa74476443119a942de498590fe1f2454d7d4ac0d?a=0x0536806df512d6cdde913cf95c9886f65b1d3462

完整代码

Commands

  1. solc --abi erc20.sol
  2. abigen --abi=erc20_sol_ERC20.abi --pkg=token --out=erc20.go

erc20.sol

  1. pragma solidity ^0.4.24;
  3. contract ERC20 {
  4.     string public constant name = "";
  5.     string public constant symbol = "";
  6.     uint8 public constant decimals = 0;
  8.     function totalSupply() public constant returns (uint);
  9.     function balanceOf(address tokenOwner) public constant returns (uint balance);
  10.     function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
  11.     function transfer(address to, uint tokens) public returns (bool success);
  12.     function approve(address spender, uint tokens) public returns (bool success);
  13.     function transferFrom(address from, address to, uint tokens) public returns (bool success);
  15.     event Transfer(address indexed from, address indexed to, uint tokens);
  16.     event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
  17. }

contract_read_erc20.go

  1. package main
  3. import (
  4.     "fmt"
  5.     "log"
  6.     "math"
  7.     "math/big"
  9.     "github.com/ethereum/go-ethereum/accounts/abi/bind"
  10.     "github.com/ethereum/go-ethereum/common"
  11.     "github.com/ethereum/go-ethereum/ethclient"
  13.     token "./contracts_erc20" // for demo
  14. )
  16. func main() {
  17.     client, err := ethclient.Dial("https://mainnet.infura.io")
  18.     if err != nil {
  19.         log.Fatal(err)
  20.     }
  22.     // Golem (GNT) Address
  23.     tokenAddress := common.HexToAddress("0xa74476443119A942dE498590Fe1f2454d7D4aC0d")
  24.     instance, err := token.NewToken(tokenAddress, client)
  25.     if err != nil {
  26.         log.Fatal(err)
  27.     }
  29.     address := common.HexToAddress("0x0536806df512d6cdde913cf95c9886f65b1d3462")
  30.     bal, err := instance.BalanceOf(&bind.CallOpts{}, address)
  31.     if err != nil {
  32.         log.Fatal(err)
  33.     }
  35.     name, err := instance.Name(&bind.CallOpts{})
  36.     if err != nil {
  37.         log.Fatal(err)
  38.     }
  40.     symbol, err := instance.Symbol(&bind.CallOpts{})
  41.     if err != nil {
  42.         log.Fatal(err)
  43.     }
  45.     decimals, err := instance.Decimals(&bind.CallOpts{})
  46.     if err != nil {
  47.         log.Fatal(err)
  48.     }
  50.     fmt.Printf("name: %s\n", name)         // "name: Golem Network"
  51.     fmt.Printf("symbol: %s\n", symbol)     // "symbol: GNT"
  52.     fmt.Printf("decimals: %v\n", decimals) // "decimals: 18"
  54.     fmt.Printf("wei: %s\n", bal) // "wei: 74605500647408739782407023"
  56.     fbal := new(big.Float)
  57.     fbal.SetString(bal.String())
  58.     value := new(big.Float).Quo(fbal, big.NewFloat(math.Pow10(int(decimals))))
  60.     fmt.Printf("balance: %f", value) // "balance: 74605500.647409"
  61. }

solc version used for these examples

  1. $ solc --version
  2. 0.4.24+commit.e67f0147.Emscripten.clang