（4）授权转账——授权接口
通过授权转账，调用方可以授权指定账户，从其地址中安全的消费指定数量的代币。
需完善合约存储：
#[ink(storage)] struct Erc20 { ...... // (代币所有者, 代币授权使用者) -> 代币授权使用者可支配余额 allowances: storage::HashMap<(AccountId, AccountId), Balance>, }
#[ink(message)] fn approve(&mut self, spender: AccountId, value: Balance) -> bool { let owner = self.env().caller(); // 代币所有者(owner)授权代币使用者(spender)可支配余额(value) self.allowances.insert((owner, spender), value); true }
（5）授权转账——余额查询
获取代币授权使用者剩余被允许转移的代币数量。
#[ink(message)] fn allowance(&self, owner: AccountId, spender: AccountId) -> Balance { self.allowance_of_or_zero(&owner, &spender) }
（6）授权转账——转账接口
允许
3.7 完整代码
#![cfg_attr(not(feature = "std"), no_std)] use ink_lang as ink; #[ink::contract(version = "0.1.0")] mod erc20 { use ink_core::storage; #[ink(storage)] struct Erc20 { /// The total supply. total_supply: storage::Value<Balance>, /// The balance of each user. balances: storage::HashMap<AccountId, Balance>, /// Approval spender on behalf of the message's sender. allowances: storage::HashMap<(AccountId, AccountId), Balance>, } #[ink(event)] struct Transfer { #[ink(topic)] from: Option<AccountId>, #[ink(topic)] to: Option<AccountId>, #[ink(topic)] value: Balance, } #[ink(event)] struct Approval { #[ink(topic)] owner: AccountId, #[ink(topic)] spender: AccountId, #[ink(topic)] value: Balance, } impl Erc20 { #[ink(constructor)] fn new(&mut self, initial_supply: Balance) { let caller = self.env().caller(); self.total_supply.set(initial_supply); self.balances.insert(caller, initial_supply); self.env().emit_event(Transfer { from: None, to: Some(caller), value: initial_supply, }); } #[ink(message)] fn total_supply(&self) -> Balance { *self.total_supply } #[ink(message)] fn balance_of(&self, owner: AccountId) -> Balance { self.balance_of_or_zero(&owner) } #[ink(message)] fn approve(&mut self, spender: AccountId, value: Balance) -> bool { let owner = self.env().caller(); self.allowances.insert((owner, spender), value); self.env().emit_event(Approval { owner, spender, value, }); true } #[ink(message)] fn allowance(&self, owner: AccountId, spender: AccountId) -> Balance { self.allowance_of_or_zero(&owner, &spender) } #[ink(message)] fn transfer_from(&mut self, from: AccountId, to: AccountId, value: Balance) -> bool { let caller = self.env().caller(); let allowance = self.allowance_of_or_zero(&from, &caller); if allowance < value { return false } self.allowances.insert((from, caller), allowance - value); self.transfer_from_to(from, to, value) } #[ink(message)] fn transfer(&mut self, to: AccountId, value: Balance) -> bool { let from = self.env().caller(); self.transfer_from_to(from, to, value) } fn transfer_from_to(&mut self, from: AccountId, to: AccountId, value: Balance) -> bool { let from_balance = self.balance_of_or_zero(&from); if from_balance < value { return false } let to_balance = self.balance_of_or_zero(&to); self.balances.insert(from, from_balance - value); self.balances.insert(to, to_balance + value); self.env().emit_event(Transfer { from: Some(from), to: Some(to), value, }); true } fn balance_of_or_zero(&self, owner: &AccountId) -> Balance { *self.balances.get(owner).unwrap_or(&0) } fn allowance_of_or_zero(&self, owner: &AccountId, spender: &AccountId) -> Balance { *self.allowances.get(&(*owner, *spender)).unwrap_or(&0) } } #[cfg(test)] mod tests { use super::*; #[test] fn new_works() { let contract = Erc20::new(777); assert_eq!(contract.total_supply(), 777); } #[test] fn balance_works() { let contract = Erc20::new(100); assert_eq!(contract.total_supply(), 100); assert_eq!(contract.balance_of(AccountId::from([0x1; 32])), 100); assert_eq!(contract.balance_of(AccountId::from([0x0; 32])), 0); } #[test] fn transfer_works() { let mut contract = Erc20::new(100); assert_eq!(contract.balance_of(AccountId::from([0x1; 32])), 100); assert!(contract.transfer(AccountId::from([0x0; 32]), 10)); assert_eq!(contract.balance_of(AccountId::from([0x0; 32])), 10); assert!(!contract.transfer(AccountId::from([0x0; 32]), 100)); } #[test] fn transfer_from_works() { let mut contract = Erc20::new(100); assert_eq!(contract.balance_of(AccountId::from([0x1; 32])), 100); contract.approve(AccountId::from([0x1; 32]), 20); contract.transfer_from(AccountId::from([0x1; 32]), AccountId::from([0x0; 32]), 10); assert_eq!(contract.balance_of(AccountId::from([0x0; 32])), 10); } } }
4 ERC20合约部署
4.1 启动substrate链
[Jason@RUAN:~/Blockchain/substrate] (v2.0.0-rc4)$ ./target/release/substrate purge-chain --dev Are you sure to remove "/root/.local/share/substrate/chains/dev/db"? [y/N]: y "/root/.local/share/substrate/chains/dev/db" did not exist. [Jason@RUAN:~/Blockchain/substrate] (v2.0.0-rc4)$ ./target/release/substrate --dev --ws-external --rpc-external --rpc-cors=all 2020-07-13 23:07:17 Substrate Node 2020-07-13 23:07:17 ✌️ version 2.0.0-rc4-00768a1-x86_64-linux-gnu 2020-07-13 23:07:17 ❤️ by Parity Technologies <admin@parity.io>, 2017-2020 2020-07-13 23:07:17 📋 Chain specification: Development 2020-07-13 23:07:17 🏷 Node name: ill-hen-8567 2020-07-13 23:07:17 👤 Role: AUTHORITY 2020-07-13 23:07:17 💾 Database: RocksDb at /root/.local/share/substrate/chains/dev/db 2020-07-13 23:07:17 ⛓ Native runtime: node-254 (substrate-node-0.tx1.au10) 2020-07-13 23:07:17 💸 new validator set of size 1 has been elected via ElectionCompute::OnChain for era 0 2020-07-13 23:07:17 🔨 Initializing Genesis block/state (state: 0xc720…bb8a, header-hash: 0x6ea2…1245) 2020-07-13 23:07:17 👴 Loading GRANDPA authority set from genesis on what appears to be first startup. 2020-07-13 23:07:17 ⏱ Loaded block-time = 3000 milliseconds from genesis on first-launch 2020-07-13 23:07:17 👶 Creating empty BABE epoch changes on what appears to be first startup. 2020-07-13 23:07:17 📦 Highest known block at #0 2020-07-13 23:07:17 Using default protocol ID "sup" because none is configured in the chain specs 2020-07-13 23:07:17 🏷 Local node identity is: 12D3KooWQUQtujJ5SGCdCcheuExioC81R5W4E3RFGhmhx3MT8iqy (legacy representation: QmX71wUqWKy7FQX8PEHKoQLaiBLLTfK8TL25mFXxKhMWGw) 2020-07-13 23:07:17 〽 Prometheus server started at 127.0.0.1:9615 2020-07-13 23:07:17 👶 Starting BABE Authorship worker 2020-07-13 23:07:18 🙌 Starting consensus session on top of parent 0x6ea2a97a8da973976a82f053a8b909aff5e0659ca6d51b6c9d6947b4dc3d1245 2020-07-13 23:07:18 🎁 Prepared block for proposing at 1 [hash: 0x3b99b664d0a21fbc72bfed709700b5bba05564c8d62e9ddd677412896f25de31; parent_hash: 0x6ea2…1245; extrinsics (1): [0xdcda…fb8d]] 2020-07-13 23:07:18 🔖 Pre-sealed block for proposal at 1. Hash now 0x3081484a5cbe82a9b4a4aea4d360fd69219a43d18182c6fd297e2ffac71feff2, previously 0x3b99b664d0a21fbc72bfed709700b5bba05564c8d62e9ddd677412896f25de31. 2020-07-13 23:07:18 👶 New epoch 0 launching at block 0x3081…eff2 (block slot 531550946 >= start slot 531550946). 2020-07-13 23:07:18 👶 Next epoch starts at slot 531551146 2020-07-13 23:07:18 ✨ Imported #1 (0x3081…eff2) 2020-07-13 23:07:21 🙌 Starting consensus session on top of parent 0x3081484a5cbe82a9b4a4aea4d360fd69219a43d18182c6fd297e2ffac71feff2 2020-07-13 23:07:21 🎁 Prepared block for proposing at 2 [hash: 0x346204e0b46b86dc4ec85b18cf2fdf0f0e818b24208e56217e6f44c135e3aef3; parent_hash: 0x3081…eff2; extrinsics (1): [0xfdbb…bdd0]] 2020-07-13 23:07:21 🔖 Pre-sealed block for proposal at 2. Hash now 0x906f64c7a6139ad0819f6c31d776404573e72f3f155bab486a9aeca7c89df810, previously 0x346204e0b46b86dc4ec85b18cf2fdf0f0e818b24208e56217e6f44c135e3aef3. 2020-07-13 23:07:21 ✨ Imported #2 (0x906f…f810)
4.2 合约编译
$ cargo contract build [1/4] Collecting crate metadata [2/4] Building cargo project Finished release [optimized] target(s) in 0.05s [3/4] Post processing wasm file [4/4] Optimizing wasm file wasm-opt is not installed. Install this tool on your system in order to reduce the size of your contract's Wasm binary. See https://github.com/WebAssembly/binaryen#tools Your contract is ready. You can find it here: ./erc20/target/erc20.wasm
4.3 metadata生成
以便通过polkadot.js.org与合约进行交互
$ cargo contract generate-metadata Generating metadata Updating git repository `https://github.com/paritytech/ink` Updating crates.io index Updating git repository `https://github.com/type-metadata/type-metadata.git` Finished release [optimized] target(s) in 3.38s Running `target/release/abi-gen` Your metadata file is ready. You can find it here: ./erc20/target/metadata.json
4.4 上传WASM
4.5 部署合约
5 ERC20合约执行
5.1 执行合约
注：右下角开关
打开开关：作为RPC调用发送，只能查看链上状态
关闭开关：作为交易发送，对链上状态有更改
5.2 查询发行总量
5.3 查询Alice账户余额
5.4 Alice给Bob转账1000
5.5 分别查询Alice和Bob余额
5.6 Alice授权Eve可以消费自己的2000代币
5.7 Eve给Ferdie转账Alice的500代币
5.8 查看到Ferdie的代币数
5.9 查看Eve剩余Alice的授权额度
6 参考资料
https://substrate.dev/substrate-contracts-workshop/#/
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