在Substrate链上跑Solidity ERC20智能合约

本实践案例中，我们首先会搭建和启动一条substrate链，再通过MetaMask这款著名的以太坊钱包浏览器插件，通过自定义RPC的方式，接入我们搭建好的substrate链。 然后我们会在remix这款智能合约在线IDE上的完成ERC20智能合约的开发、编译、部署、调试。remix将通过Injected Web3的方式接入我们的MetaMask钱包，借助MetaMask实现和substrate链的交互。

**在Substrate链上跑Solidity ERC20智能合约** *jasonruan 2020.07.18* ## 1 前言 本实践案例中，我们首先会搭建和启动一条`substrate`链，再通过`MetaMask`这款著名的以太坊钱包浏览器插件，通过自定义`RPC`的方式，接入我们搭建好的`substrate`链。 然后我们会在`remix`这款智能合约在线`IDE`上的完成`ERC20`智能合约的开发、编译、部署、调试。`remix`将通过`Injected Web3`的方式接入我们的`MetaMask`钱包，借助`MetaMask`实现和`substrate`链的交互。 ## 2 前置准备 ### 2.1 substrate链启动 > 由于[Substrate](https://github.com/paritytech/substrate)的`runtime`没有集成`EVM`，需要使用`Parity`另外一个项目：[Frontier](https://github.com/paritytech/frontier)。`Frontier`是`Substrate`的以太坊兼容层。 > > 在这个项目中，增加了`pallet-evm`、`pallet-ethereum`、`rpc-ethereum`，可以最大程度的模拟以太坊的环境，以便可以无缝对接当前以太坊生态里面`DApp`及第三方工具，如`remix`、`metamask`等。 > >  > #### 2.1.1 安装 ```bash $ git clone git@github.com:paritytech/frontier.git $ cd frontier (master)$ git log commit fcea97281661f0a0a4c28e46edbfb1238043471e Author: Wei Tang <wei@that.world> Date: Tue Jul 14 13:25:48 2020 +0200 (master)$ git submodule init 子模组 'vendor/ethereum' (https://github.com/rust-blockchain/ethereum) 已为路径 'vendor/ethereum' 注册 子模组 'vendor/evm' (https://github.com/rust-blockchain/evm) 已为路径 'vendor/evm' 注册 子模组 'vendor/substrate' (https://github.com/paritytech/substrate) 已为路径 'vendor/substrate' 注册 (master)$ git submodule update 正克隆到 'vendor/ethereum'... 处理 delta 中: 100% (930/930), done. 子模组路径 'vendor/ethereum'：检出 '4fdd3c8ac849f91f5352bc7dfc189144a09aac1e' 正克隆到 'vendor/evm'... 子模组路径 'vendor/evm'：检出 '84013f3ea23e436541f409c717134dd1536143de' 正克隆到 'vendor/substrate'... fatal: 引用不是一个树：b36fc2c849ae0cba434bb3ce82e0a4dda5bcbe7a 无法在子模组路径 'vendor/substrate' 中检出 'b36fc2c849ae0cba434bb3ce82e0a4dda5bcbe7a' # 获取子模块有报错，单独clone substrate工程来解决 $ cd vendor $ /bin/rm -rf substrate $ git clone git@github.com:paritytech/substrate.git # 注意：这里不能切换到最新的tag（v2.0.0-rc4），编译会报错，采用当前最新的master分支，可以正常编译frontier [Jason@RUAN:~/frontier/vendor/substrate] (master)$ git log commit 9b5a9cb9056f8ab049837d30b500fca78a6c362c Author: Shawn Tabrizi <shawntabrizi@gmail.com> Date: Thu Jul 16 02:21:15 2020 +0200 ``` #### 2.1.2 添加个人账号 > 在substrate frontier链的创世配置里面，内建我们在MetaMask上的自有账号，并初始化配置上足够的ETH数量，以便我们开发测试的需要。 - 拷贝个人测试账号地址 > `0x888a0bF014d1D6334002261BaC34a16f5Ce963ac`  - 修改`frontier/template/node/src/chain_spec.rs`，添加以下内容： ```rust + 29 use std::str::FromStr; ! 141 let built_in_evm_account = ! 142 H160::from_str("888a0bF014d1D6334002261BaC34a16f5Ce963ac").unwrap(); ! 143 let mut evm_accounts = BTreeMap::new(); ! 144 //let ten: u128 = 10; ! 145 evm_accounts.insert( ! 146 built_in_evm_account, ! 147 evm::GenesisAccount { ! 148 nonce: 0.into(), ! 149 balance: (2018030320150719 as u128 * 10_u128.pow(18)).into(), // 设置账户初始ETH余额，注意ETH有18位小数 ! 150 storage: BTreeMap::new(), ! 151 code: WASM_BINARY.to_vec(), ! 152 }, ! 153 ); ``` #### 2.1.3 编译 ```bash $ cargo build --release ``` #### 2.1.4 运行 ```bash (master)$ ./target/release/frontier-template-node purge-chain --dev Are you sure to remove "/root/.local/share/frontier-template-node/chains/dev/db"? [y/N]: y "/root/.local/share/frontier-template-node/chains/dev/db" did not exist. (master)$ ./target/release/frontier-template-node --dev --ws-external --rpc-external --rpc-cors=all 2020-07-18 22:59:28 Substrate Node 2020-07-18 22:59:28 ️ version 2.0.0-dev-fcea972-x86_64-linux-gnu 2020-07-18 22:59:28 ️ by Parity Technologies <admin@parity.io>, 2017-2020 2020-07-18 22:59:28 Chain specification: Development 2020-07-18 22:59:28 Node name: stimulating-hand-5352 2020-07-18 22:59:28 Role: AUTHORITY 2020-07-18 22:59:28 Database: RocksDb at /root/.local/share/frontier-template-node/chains/dev/db 2020-07-18 22:59:28 Native runtime: node-frontier-template-1 (node-frontier-template-1.tx1.au1) 2020-07-18 22:59:28 Initializing Genesis block/state (state: 0x1e15…857d, header-hash: 0xa26e…22df) 2020-07-18 22:59:28 Loading GRANDPA authority set from genesis on what appears to be first startup. 2020-07-18 22:59:29 ⏱ Loaded block-time = 6000 milliseconds from genesis on first-launch 2020-07-18 22:59:29 Highest known block at #0 2020-07-18 22:59:29 Using default protocol ID "sup" because none is configured in the chain specs 2020-07-18 22:59:29 Local node identity is: 12D3KooWMgcWheT7cvvpaaKmqNLVPRpAkGLR9V1M7pfs43DxZU6c (legacy representation: QmRN3jaSxZV5dMk1P5tm1CB9oud8pU8SGZvrUFfuS9dNMQ) 2020-07-18 22:59:29 〽️ Prometheus server started at 127.0.0.1:9615 2020-07-18 22:59:30 Starting consensus session on top of parent 0xa26e0b7f2abed8a4bcf87ca45d20d7628cf22225dd522385e7b49ee6c30522df 2020-07-18 22:59:30 Prepared block for proposing at 1 [hash: 0xd3558be2df939b94ba94d82ded332216b0b06a55596d0a61a858aeaf7acc16c4; parent_hash: 0xa26e…22df; extrinsics (1): [0xead1…ac1b]] 2020-07-18 22:59:30 Pre-sealed block for proposal at 1. Hash now 0x8aa38d1228213371249ff83404bd8576e3e0bce6e120f93a9fe08ec2dfdc2d86, previously 0xd3558be2df939b94ba94d82ded332216b0b06a55596d0a61a858aeaf7acc16c4. 2020-07-18 22:59:30 Imported #1 (0x8aa3…2d86) 2020-07-18 22:59:34 Idle (0 peers), best: #1 (0x8aa3…2d86), finalized #0 (0xa26e…22df), ⬇ 0 ⬆ 0 2020-07-18 22:59:36 Starting consensus session on top of parent 0x8aa38d1228213371249ff83404bd8576e3e0bce6e120f93a9fe08ec2dfdc2d86 2020-07-18 22:59:36 Prepared block for proposing at 2 [hash: 0x570be59726cf2018fab9e7bae77208a990921291fe8164bbc1df253f8142d3f6; parent_hash: 0x8aa3…2d86; extrinsics (1): [0xec7f…0d17]] 2020-07-18 22:59:36 Pre-sealed block for proposal at 2. Hash now 0xe9831c239f29745d79b0e72cc26c0db19ce4d0c7712a32dae4cc60f8ad538551, previously 0x570be59726cf2018fab9e7bae77208a990921291fe8164bbc1df253f8142d3f6. 2020-07-18 22:59:36 Imported #2 (0xe983…8551) ``` ### 2.2 MetaMask接入frontier链 #### 2.2.1 配置自定义RPC接入 > 这里`ChainID`填42，源于`runtime`中的定义： > > ```rust > parameter_types! { > pub const EVMModuleId: ModuleId = ModuleId(*b"py/evmpa"); > pub const ChainId: u64 = 42; > } > > impl evm::Trait for Runtime { > type ModuleId = EVMModuleId; > type FeeCalculator = FixedGasPrice; > type ConvertAccountId = HashTruncateConvertAccountId<BlakeTwo256>; > type Currency = Balances; > type Event = Event; > type Precompiles = (); > type ChainId = ChainId; > } > ```  #### 2.2.2 查看账户余额  #### 2.2.3 开启Gas控制高级选项 > 开启该选项后，以便我们随意配置`gas limit`和`gas price`：  ### 2.3 remix接入MetaMask - 使用`Injected Web3`建立与`MetaMask`账号的连接  我们看到我们创建的账号已经成功接入`remix`，接下来，我们便可以进行`ERC20`合约的开发和部署了。 ## 3 合约开发&部署 ### 3.1 智能合约编写 我们要编写两个合约，其中`SafeMath.sol`是一个算数运算防溢出的安全库，`xyc.sol`是一个`ERC20`智能合约。 #### 3.1.1 SafeMath.sol ```js pragma solidity ^0.6.0; library SafeMath { function add(uint256 a, uint256 b) internal pure returns (uint256) { uint256 c = a + b; require(c >= a, "SafeMath: addition overflow"); return c; } function sub(uint256 a, uint256 b) internal pure returns (uint256) { return sub(a, b, "SafeMath: subtraction overflow"); } function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { require(b <= a, errorMessage); uint256 c = a - b; return c; } function mul(uint256 a, uint256 b) internal pure returns (uint256) { if (a == 0) { return 0; } require(c / a == b, "SafeMath: multiplication overflow"); return c; } function div(uint256 a, uint256 b) internal pure returns (uint256) { return div(a, b, "SafeMath: division by zero"); } function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { require(b > 0, errorMessage); uint256 c = a / b; return c; } function mod(uint256 a, uint256 b) internal pure returns (uint256) { return mod(a, b, "SafeMath: modulo by zero"); } function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { require(b != 0, errorMessage); return a % b; } } ``` #### 3.1.2 xyc.sol ```js pragma solidity ^0.6.0; import "./SafeMath.sol"; abstract contract ERC20 { function totalSupply() public virtual view returns (uint256); function balanceOf(address owner) public virtual view returns (uint256); function transfer(address to, uint256 value) public virtual returns (bool); function transferFrom(address from, address to, uint256 value) public virtual returns (bool); function approve(address spender, uint256 value) public virtual returns (bool); function allowance(address owner, address spender) public virtual view returns (uint256); event Transfer(address indexed from, address indexed to, uint256 value); event Approval(address indexed owner, address indexed spender, uint256 value); } contract xyc is ERC20 { using SafeMath for uint256; string name = "XuanYuan Coin"; string symbol = "xyc"; uint8 decimals; uint256 private _totalSupply; mapping(address => uint256) private _balances; mapping(address => mapping(address => uint256)) private _allowances; constructor(uint256 myTotalSupply, uint8 mydecimals) public { _totalSupply = myTotalSupply; decimals = mydecimals; _balances[msg.sender] = myTotalSupply; } function totalSupply() public override view returns (uint256) { return _totalSupply; } function balanceOf(address _owner) public override view returns (uint256) { return _balances[_owner]; } function transfer(address to, uint256 value) public override returns (bool) { require(to != address(0), "ERC20 ERROR: transfer from zero address"); require(value <= _balances[msg.sender]); require(_balances[to] + value >= _balances[to]); _balances[msg.sender] = _balances[msg.sender].sub(value); _balances[to] = _balances[to].add(value); emit Transfer(msg.sender, to, value); return true; } function transferFrom(address from, address to, uint256 value) public override returns (bool) { require(to != address(0)); require(value <= _balances[from]); require(value <= _allowances[from][msg.sender]); require(_balances[to] + value >= _balances[to]); _balances[from] = _balances[from].sub(value); _balances[to] = _balances[to].add(value); _allowances[from][msg.sender] = _allowances[from][msg.sender].sub(value); emit Transfer(from, to, value); return true; } function approve(address spender, uint256 value) public override returns (bool) { require(value <= _balances[msg.sender]); _allowances[msg.sender][spender] = value; emit Approval(msg.sender, spender, value); return true; } function allowance(address _owner, address spender) public override view returns (uint256) { return _allowances[_owner][spender]; } event Transfer(address indexed from, address indexed to, uint256 value); event Approval(address indexed owner, address indexed spender, uint256 value); } ``` ### 3.2 智能合约编译  智能合约编译成功，接下来我们就将已经开发完成的`Solidity ERC20`智能合约部署到`Substrate`链上。 ### 3.3 智能合约部署 - 选择要部署的合约，填写构造方法中的发行总量和精度两个参数，点击`transact`按钮 > 注：当前版本需要在弹出的MetaMask对话框上，设置很大的gas limit值（`4294967295`）才能部署成功:(  ## 4 合约功能测试 通过`remix`完成对`ERC20`合约的功能测试。 ### 4.1 查看发行量&余额  可见所有发行代币都归属于合约部署方地址。 ### 4.2 转账测试 - 给账户2：`0x8A832874304Be72b299C0ED96f22B11311c9051C`，转账1000.00 XYC，查看账户1地址XYC代币数量为：9000.00，符合预期  - 在MetaMask上添加自定义代币 > 合约地址：`0xfE2dF1EE3783eBD46481e32d849acB49ec5004Bf`  - 代币发行方地址所剩代币为：9000.00 XYC  - 代币接收方地址代币数量为：1000.00 XYC  ### 4.3 授权代理转账测试 - 为账户2转账ETH，用于支付gas费   - 用户1授权用户2可代理转账的代币数量为2000.00 XYC  - 查看用户2所能授权转账用户1的XYC代币 | 账号 | 地址 | | --------- | -------------------------------------------- | | Jasonruan | `0x888a0bF014d1D6334002261BaC34a16f5Ce963ac` | | Account 2 | `0x8A832874304Be72b299C0ED96f22B11311c9051C` | | Account 3 | `0x6Be02d1d3665660d22FF9624b7BE0551ee1Ac91b` |  - 用户2代理用户1给用户3转账2000.00 XYC > 成功转账后，查看到用户2所能授权转账用户1的XYC代币数量为0  - 查看到账户3上XYC代币余额  - 再次查看账户1上的代币余额 

在Substrate链上跑Solidity ERC20智能合约

jasonruan 2020.07.18

1 前言

本实践案例中，我们首先会搭建和启动一条substrate链，再通过MetaMask这款著名的以太坊钱包浏览器插件，通过自定义RPC的方式，接入我们搭建好的substrate链。

然后我们会在remix这款智能合约在线IDE上的完成ERC20智能合约的开发、编译、部署、调试。remix将通过Injected Web3的方式接入我们的MetaMask钱包，借助MetaMask实现和substrate链的交互。

2 前置准备

2.1 substrate链启动

由于Substrate的runtime没有集成EVM，需要使用Parity另外一个项目：Frontier。Frontier是Substrate的以太坊兼容层。

在这个项目中，增加了pallet-evm、pallet-ethereum、rpc-ethereum，可以最大程度的模拟以太坊的环境，以便可以无缝对接当前以太坊生态里面DApp及第三方工具，如remix、metamask等。

2.1.1 安装

$ git clone git@github.com:paritytech/frontier.git

$ cd frontier

(master)$ git log
commit fcea97281661f0a0a4c28e46edbfb1238043471e
Author: Wei Tang <wei@that.world>
Date:   Tue Jul 14 13:25:48 2020 +0200

(master)$ git submodule init
子模组 'vendor/ethereum' (https://github.com/rust-blockchain/ethereum) 已为路径 'vendor/ethereum' 注册
子模组 'vendor/evm' (https://github.com/rust-blockchain/evm) 已为路径 'vendor/evm' 注册
子模组 'vendor/substrate' (https://github.com/paritytech/substrate) 已为路径 'vendor/substrate' 注册

(master)$ git submodule update
正克隆到 'vendor/ethereum'...
处理 delta 中: 100% (930/930), done.
子模组路径 'vendor/ethereum'：检出 '4fdd3c8ac849f91f5352bc7dfc189144a09aac1e'
正克隆到 'vendor/evm'...
子模组路径 'vendor/evm'：检出 '84013f3ea23e436541f409c717134dd1536143de'
正克隆到 'vendor/substrate'...
fatal: 引用不是一个树：b36fc2c849ae0cba434bb3ce82e0a4dda5bcbe7a
无法在子模组路径 'vendor/substrate' 中检出 'b36fc2c849ae0cba434bb3ce82e0a4dda5bcbe7a'

# 获取子模块有报错，单独clone substrate工程来解决
$ cd vendor
$ /bin/rm -rf substrate
$ git clone git@github.com:paritytech/substrate.git

# 注意：这里不能切换到最新的tag（v2.0.0-rc4），编译会报错，采用当前最新的master分支，可以正常编译frontier
[Jason@RUAN:~/frontier/vendor/substrate] (master)$ git log
commit 9b5a9cb9056f8ab049837d30b500fca78a6c362c
Author: Shawn Tabrizi <shawntabrizi@gmail.com>
Date:   Thu Jul 16 02:21:15 2020 +0200

2.1.2 添加个人账号

在substrate frontier链的创世配置里面，内建我们在MetaMask上的自有账号，并初始化配置上足够的ETH数量，以便我们开发测试的需要。

• 拷贝个人测试账号地址

  0x888a0bF014d1D6334002261BaC34a16f5Ce963ac

• 修改frontier/template/node/src/chain_spec.rs，添加以下内容：

+  29 use std::str::FromStr;

! 141         let built_in_evm_account =
! 142             H160::from_str("888a0bF014d1D6334002261BaC34a16f5Ce963ac").unwrap();
! 143         let mut evm_accounts = BTreeMap::new();
! 144         //let ten: u128 = 10;
! 145         evm_accounts.insert(
! 146             built_in_evm_account,
! 147             evm::GenesisAccount {
! 148                 nonce: 0.into(),
! 149                 balance: (2018030320150719 as u128 * 10_u128.pow(18)).into(),    // 设置账户初始ETH余额，注意ETH有18位小数
! 150                 storage: BTreeMap::new(),                                 
! 151                 code: WASM_BINARY.to_vec(),
! 152             },  
! 153         );  

2.1.3 编译

$ cargo build --release

2.1.4 运行

(master)$ ./target/release/frontier-template-node purge-chain --dev
Are you sure to remove "/root/.local/share/frontier-template-node/chains/dev/db"? [y/N]: y
"/root/.local/share/frontier-template-node/chains/dev/db" did not exist.

(master)$ ./target/release/frontier-template-node  --dev --ws-external --rpc-external --rpc-cors=all
2020-07-18 22:59:28 Substrate Node
2020-07-18 22:59:28 ️  version 2.0.0-dev-fcea972-x86_64-linux-gnu
2020-07-18 22:59:28 ️  by Parity Technologies <admin@parity.io>, 2017-2020
2020-07-18 22:59:28  Chain specification: Development
2020-07-18 22:59:28   Node name: stimulating-hand-5352
2020-07-18 22:59:28  Role: AUTHORITY
2020-07-18 22:59:28  Database: RocksDb at /root/.local/share/frontier-template-node/chains/dev/db
2020-07-18 22:59:28   Native runtime: node-frontier-template-1 (node-frontier-template-1.tx1.au1)
2020-07-18 22:59:28  Initializing Genesis block/state (state: 0x1e15…857d, header-hash: 0xa26e…22df)
2020-07-18 22:59:28  Loading GRANDPA authority set from genesis on what appears to be first startup.
2020-07-18 22:59:29 ⏱  Loaded block-time = 6000 milliseconds from genesis on first-launch
2020-07-18 22:59:29  Highest known block at #0
2020-07-18 22:59:29 Using default protocol ID "sup" because none is configured in the chain specs
2020-07-18 22:59:29   Local node identity is: 12D3KooWMgcWheT7cvvpaaKmqNLVPRpAkGLR9V1M7pfs43DxZU6c (legacy representation: QmRN3jaSxZV5dMk1P5tm1CB9oud8pU8SGZvrUFfuS9dNMQ)
2020-07-18 22:59:29 〽️ Prometheus server started at 127.0.0.1:9615
2020-07-18 22:59:30  Starting consensus session on top of parent 0xa26e0b7f2abed8a4bcf87ca45d20d7628cf22225dd522385e7b49ee6c30522df
2020-07-18 22:59:30  Prepared block for proposing at 1 [hash: 0xd3558be2df939b94ba94d82ded332216b0b06a55596d0a61a858aeaf7acc16c4; parent_hash: 0xa26e…22df; extrinsics (1): [0xead1…ac1b]]
2020-07-18 22:59:30  Pre-sealed block for proposal at 1. Hash now 0x8aa38d1228213371249ff83404bd8576e3e0bce6e120f93a9fe08ec2dfdc2d86, previously 0xd3558be2df939b94ba94d82ded332216b0b06a55596d0a61a858aeaf7acc16c4.
2020-07-18 22:59:30  Imported #1 (0x8aa3…2d86)
2020-07-18 22:59:34  Idle (0 peers), best: #1 (0x8aa3…2d86), finalized #0 (0xa26e…22df), ⬇ 0 ⬆ 0
2020-07-18 22:59:36  Starting consensus session on top of parent 0x8aa38d1228213371249ff83404bd8576e3e0bce6e120f93a9fe08ec2dfdc2d86
2020-07-18 22:59:36  Prepared block for proposing at 2 [hash: 0x570be59726cf2018fab9e7bae77208a990921291fe8164bbc1df253f8142d3f6; parent_hash: 0x8aa3…2d86; extrinsics (1): [0xec7f…0d17]]
2020-07-18 22:59:36  Pre-sealed block for proposal at 2. Hash now 0xe9831c239f29745d79b0e72cc26c0db19ce4d0c7712a32dae4cc60f8ad538551, previously 0x570be59726cf2018fab9e7bae77208a990921291fe8164bbc1df253f8142d3f6.
2020-07-18 22:59:36  Imported #2 (0xe983…8551)

2.2 MetaMask接入frontier链

2.2.1 配置自定义RPC接入

这里ChainID填42，源于runtime中的定义：

parameter_types! {
    pub const EVMModuleId: ModuleId = ModuleId(*b"py/evmpa");
    pub const ChainId: u64 = 42; 
}

impl evm::Trait for Runtime {
    type ModuleId = EVMModuleId;
    type FeeCalculator = FixedGasPrice;
    type ConvertAccountId = HashTruncateConvertAccountId<BlakeTwo256>;
    type Currency = Balances;
    type Event = Event;
    type Precompiles = (); 
    type ChainId = ChainId;
}

2.2.2 查看账户余额

2.2.3 开启Gas控制高级选项

开启该选项后，以便我们随意配置gas limit和gas price：

2.3 remix接入MetaMask

• 使用Injected Web3建立与MetaMask账号的连接

我们看到我们创建的账号已经成功接入remix，接下来，我们便可以进行ERC20合约的开发和部署了。

3 合约开发&部署

3.1 智能合约编写

我们要编写两个合约，其中SafeMath.sol是一个算数运算防溢出的安全库，xyc.sol是一个ERC20智能合约。

3.1.1 SafeMath.sol

pragma solidity ^0.6.0;

library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

3.1.2 xyc.sol

pragma solidity ^0.6.0;

import "./SafeMath.sol";

abstract contract ERC20 {
   function totalSupply() public virtual view returns (uint256);
   function balanceOf(address owner) public virtual view returns (uint256);
   function transfer(address to, uint256 value) public virtual returns (bool);
   function transferFrom(address from, address to, uint256 value) public virtual returns (bool);
   function approve(address spender, uint256 value) public virtual returns (bool);
   function allowance(address owner, address spender) public virtual view returns (uint256);
   event Transfer(address indexed from, address indexed to, uint256 value);
   event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract xyc is ERC20 {

    using SafeMath for uint256;

    string name = "XuanYuan Coin";
    string symbol = "xyc";
    uint8 decimals;
    uint256 private _totalSupply;
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    constructor(uint256 myTotalSupply, uint8 mydecimals) public {
        _totalSupply = myTotalSupply;
        decimals = mydecimals;
        _balances[msg.sender] = myTotalSupply;
    }

   function totalSupply() public override view returns (uint256) {
       return _totalSupply;
   }

   function balanceOf(address _owner) public override view returns (uint256) {
       return _balances[_owner];
   }

   function transfer(address to, uint256 value) public override returns (bool) {
       require(to != address(0), "ERC20 ERROR: transfer from zero address");
       require(value <= _balances[msg.sender]);
       require(_balances[to] + value >= _balances[to]);

       _balances[msg.sender] = _balances[msg.sender].sub(value);
       _balances[to] = _balances[to].add(value);

       emit Transfer(msg.sender, to, value);

       return true;
   }

   function transferFrom(address from, address to, uint256 value) public override returns (bool) {
       require(to != address(0));
       require(value <= _balances[from]);
       require(value <= _allowances[from][msg.sender]);
       require(_balances[to] + value >= _balances[to]);

       _balances[from] = _balances[from].sub(value);
       _balances[to] = _balances[to].add(value);
       _allowances[from][msg.sender] = _allowances[from][msg.sender].sub(value);

       emit Transfer(from, to, value);

       return true;
   }

   function approve(address spender, uint256 value) public override returns (bool) {
       require(value <= _balances[msg.sender]);
       _allowances[msg.sender][spender] = value;
       emit Approval(msg.sender, spender, value);
       return true;
   }

   function allowance(address _owner, address spender) public override view returns (uint256) {
       return _allowances[_owner][spender];
   }

   event Transfer(address indexed from, address indexed to, uint256 value);
   event Approval(address indexed owner, address indexed spender, uint256 value);
}

3.2 智能合约编译

智能合约编译成功，接下来我们就将已经开发完成的Solidity ERC20智能合约部署到Substrate链上。

3.3 智能合约部署

• 选择要部署的合约，填写构造方法中的发行总量和精度两个参数，点击transact按钮

注：当前版本需要在弹出的MetaMask对话框上，设置很大的gas limit值（4294967295）才能部署成功:(

4 合约功能测试

通过remix完成对ERC20合约的功能测试。

4.1 查看发行量&余额

可见所有发行代币都归属于合约部署方地址。

4.2 转账测试

• 给账户2：0x8A832874304Be72b299C0ED96f22B11311c9051C，转账1000.00 XYC，查看账户1地址XYC代币数量为：9000.00，符合预期

• 在MetaMask上添加自定义代币

合约地址：0xfE2dF1EE3783eBD46481e32d849acB49ec5004Bf

• 代币发行方地址所剩代币为：9000.00 XYC

• 代币接收方地址代币数量为：1000.00 XYC

4.3 授权代理转账测试

• 为账户2转账ETH，用于支付gas费

• 用户1授权用户2可代理转账的代币数量为2000.00 XYC

• 查看用户2所能授权转账用户1的XYC代币

• 用户2代理用户1给用户3转账2000.00 XYC

成功转账后，查看到用户2所能授权转账用户1的XYC代币数量为0

• 查看到账户3上XYC代币余额

• 再次查看账户1上的代币余额

区块链技术网。

• 发表于 2020-07-20 10:30
• 阅读 ( 1812 )
• 学分 ( 147 )
• 分类：Polkadot