substrate基础(13)-智能合约初体验

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初步掌握ink智能合约的使用

1. 概述

  1. substrate的合约称为ink
  2. ink！是一种嵌入式领域特定语言，可以用Rust来编写基于webassembly的智能合约。
  3. ink！实际上是一种使用#[ink(…)]属性宏标准的Rust写法。

2. 准备工作

下载带有合约功能的节点模板：

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git clone https://github.com/paritytech/substrate-contracts-node

该节点模板需要编译并启动，这个过程就不在这里阐述了，不是重点。

为了方便设置substrate智能合约，安装ink！CLI：

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#  先安装依赖工具binaryen
# For Ubuntu or Debian users
sudo apt install binaryen
# For MacOS users
brew install binaryen

# 安装合约依赖
cargo install dylint-link --force
cargo install cargo-dylint --force

# 再安装lik! cli：
cargo install cargo-contract --force
# 或者
cargo install cargo-contract --vers ^0.16 --force --locked

检测是否安装成功

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cargo contract --help

3. 模板体验

3.1 创建合约

生成合约模板(flipper表示项目名)：

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cargo contract new flipper

执行后，生成一个ink合约项目模板，官方提供了一个类似HelloWorld的案例，可以用其进一步开发合约，也可以立即部署去体验：

测试合约代码：

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cargo test
# 或者
cargo +nightly test

# nocapture表示输出测试详情
cargo +nightly test -- --nocapture

编译合约

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cargo contract build
# 或者
cargo +nightly contract build

编译好后的合约在target目录中flipper/target/ink/，其中包含一个flipper.wasm和flipper.contract文件。.contract文件就是用来部署到链上的合约文件，而wasm文件则包含合约的ABI。

3.2 部署并体验合约

启动节点：

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substrate-contracts-node --dev

打开合约用户界面 连接节点
单击“添加新合同”。
单击上传新合约代码，即上传前面生成的flipper.contract文件

具体页面上合约的调用比较简单，这里就不详细阐述了

4. 基本语法

4.1 存储类型

substrate合约可以存储使用Parity Codec编码和解码的类型，例如像bool, u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, string, 元组，数组等。另外ink！还提供substrate特定类型如AccountId，Balance，Hash等作为原始类型。

4.2 函数

  1. 合约函数
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impl MyContract {
    // Public and Private functions go here
}
  1. 构造函数
    每个ink！智能合约必须有在创建时运行一次的构造函数。每个ink！智能合约可以有多个构造函数。构造函数写法如下：
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use ink_lang as ink;

#[ink::contract]
mod mycontract {
    #[ink(storage)]
    pub struct MyContract {
        number: u32,
    }
    impl MyContract {
        /// Constructor that initializes the `u32` value to the given `init_value`.
        #[ink(constructor)]
        pub fn new(init_value: u32) -> Self {
            Self {
                number: init_value,
            }
        }

        /// Constructor that initializes the `u32` value to the `u32` default.
        ///
        /// Constructors can delegate to other constructors.
        #[ink(constructor)]
        pub fn default() -> Self {
            Self {
                number: Default::default(),
            }
        }
    /* --snip-- */
    }
}
  1. 公有函数和私有函数
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impl MyContract {
    /// Public function
    #[ink(message)]
    pub fn my_public_function(&self) {
        /* --snip-- */
    }

    /// Private function
    fn my_private_function(&self) {
        /* --snip-- */
    }
    /* --snip-- */
}
  1. 获取合约上的值
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impl MyContract {
    #[ink(message)]
    pub fn my_getter(&self) -> u32 {
        self.number
    }
}
  1. 可变和不可变的函数
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impl MyContract {
    #[ink(message)]
    pub fn my_getter(&self) -> u32 {
        self.my_number
    }

    #[ink(message)]
    pub fn my_setter(&mut self, new_value: u32) {
        self.my_number = new_value;
    }
}
  1. 惰性存储值
    当需要使用的时候，才会被加载，减少gas浪费
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#[ink(storage)]
pub struct MyContract {
    // Store some number
    my_number: ink_storage::Lazy<u32>,
}

impl MyContract {
    #[ink(constructor)]
    pub fn new(init_value: u32) -> Self {
        Self {
            my_number: ink_storage::Lazy::<u32>::new(init_value),
        }
    }

    #[ink(message)]
    pub fn my_setter(&mut self, new_value: u32) {
        ink_storage::Lazy::<u32>::set(&mut self.my_number, new_value);
    }

    #[ink(message)]
    pub fn my_adder(&mut self, add_value: u32) {
        let my_number = &mut self.my_number;
        let cur = ink_storage::Lazy::<u32>::get(my_number);
        ink_storage::Lazy::<u32>::set(my_number, cur + add_value);
    }
}
  1. mapping存储
    HashMap
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#[ink(storage)]
pub struct MyContract {
    // Store a mapping from AccountIds to a u32
    my_number_map: ink_storage::collections::HashMap<AccountId, u32>,
}

初始化一个HashMap

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#![cfg_attr(not(feature = "std"), no_std)]
use ink_lang as ink;
#[ink::contract]
mod mycontract {

    #[ink(storage)]
    pub struct MyContract {
        // Store a mapping from AccountIds to a u32
        my_number_map: ink_storage::collections::HashMap<AccountId, u32>,
    }
    impl MyContract {
        /// Public function.
        /// Default constructor.
        #[ink(constructor)]
        pub fn default() -> Self {
            Self {
                my_number_map: Default::default(),
            }
        }

        /// Private function.
        /// Returns the number for an AccountId or 0 if it is not set.
        fn my_number_or_zero(&self, of: &AccountId) -> u32 {
            let balance = self.my_number_map.get(of).unwrap_or(&0);
            *balance
        }
    }
}

修改hash map

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let caller = self.env().caller();
self.my_number_map
    .entry(caller)
    .and_modify(|old_value| *old_value += by)
    .or_insert(by);
  1. 合约调用者
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#![cfg_attr(not(feature = "std"), no_std)]

use ink_lang as ink;

#[ink::contract]
mod mycontract {

    #[ink(storage)]
    pub struct MyContract {
        // Store a contract owner
        owner: AccountId,
    }

    impl MyContract {
        #[ink(constructor)]
        pub fn new() -> Self {
            Self {
                owner: Self::env().caller();
            }
        }
        /* --snip-- */
    }
}

4. 实现ERC20智能合约

生成合约项目模板(flipper表示项目名)：

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cargo contract new erc20

lib.rs中实现erc20

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#![cfg_attr(not(feature = "std"), no_std)]

use ink_lang as ink;

#[ink::contract]
mod erc20 {
    use ink_storage::{
        traits::SpreadAllocate,
        Mapping,
    };

    /// Create storage for a simple ERC-20 contract.
    #[ink(storage)]
    #[derive(SpreadAllocate)]
    pub struct Erc20 {
        /// Total token supply.
        total_supply: Balance,
        /// Mapping from owner to number of owned tokens.
        balances: Mapping<AccountId, Balance>,
        allowances: Mapping<(AccountId, AccountId), Balance>,
    }

    #[ink(event)]
    pub struct Transfer {
        #[ink(topic)]
        from: Option<AccountId>,

        #[ink(topic)]
        to: Option<AccountId>,

        #[ink(topic)]
        value: Balance,
    }

    #[ink(event)]
    pub struct Approval {
        #[ink(topic)]
        owner: AccountId,
        #[ink(topic)]
        spender: AccountId,
        #[ink(topic)]
        value: Balance,
    }

    impl Erc20 {
        /// Create a new ERC-20 contract with an initial supply.
        #[ink(constructor)]
        pub fn new(initial_supply: Balance) -> Self {
            // Initialize mapping for the contract.
            ink_lang::utils::initialize_contract(|contract| {
                Self::new_init(contract, initial_supply)
            })
        }

        /// Initialize the ERC-20 contract with the specified initial supply.
        fn new_init(&mut self, initial_supply: Balance) {
            let caller = Self::env().caller();
            self.balances.insert(&caller, &initial_supply);
            self.total_supply = initial_supply;

            Self::env().emit_event(Transfer {
                from: None,
                to: Some(caller),
                value: initial_supply,
            });
        }

        /// Returns the total token supply.
        #[ink(message)]
        pub fn total_supply(&self) -> Balance {
            self.total_supply
        }

        /// Returns the account balance for the specified `owner`.
        #[ink(message)]
        pub fn balance_of(&self, owner: AccountId) -> Balance {
            self.balances.get(owner).unwrap_or_default()
        }

        #[ink(message)]
        pub 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)]
        pub fn allowance(&self, owner: AccountId, spender: AccountId) -> Balance {
            self.allowance_of_or_zero(&owner, &spender)
        }

        #[ink(message)]
        pub 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;
            }

            let transfer_result = self.transfer_from_to(from, to, value);
            if !transfer_result {
                return false;
            }

            self.allowances.insert((from, caller), &(&allowance - &value));
            true
        }

        #[ink(message)]
        pub fn transfer(&mut self, to: AccountId, value: Balance) -> bool {
            self.transfer_from_to(self.env().caller(), 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;
            }

            self.balances.insert(from, &(&from_balance - &value));
            let to_balance = self.balance_of_or_zero(&to);
            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_default()
        }

        fn allowance_of_or_zero(&self, owner: &AccountId, spender: &AccountId) -> Balance {
            self.allowances.get(&(*owner, *spender)).unwrap_or_default()
        }
    }

    #[cfg(test)]
    mod tests {
        use super::*;
        use ink_lang as ink;
        #[ink::test]
        fn new_works() {
            let contract = Erc20::new(888);
            assert_eq!(contract.total_supply(), 888);
        }

        #[ink::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);
        }

        #[ink::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));
        }

        #[ink::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);
        }

        #[ink::test]
        fn allowances_works() {
            let mut contract = Erc20::new(100);
            assert_eq!(contract.balance_of(AccountId::from([0x1; 32])), 100);
            contract.approve(AccountId::from([0x1; 32]), 200);
            assert_eq!(
                contract.allowance(AccountId::from([0x1; 32]), AccountId::from([0x1; 32])),
                200
            );

            assert!(contract.transfer_from(
                AccountId::from([0x1; 32]),
                AccountId::from([0x0; 32]),
                50
            ));
            assert_eq!(contract.balance_of(AccountId::from([0x0; 32])), 50);
            assert_eq!(
                contract.allowance(AccountId::from([0x1; 32]), AccountId::from([0x1; 32])),
                150
            );

            assert!(!contract.transfer_from(
                AccountId::from([0x1; 32]),
                AccountId::from([0x0; 32]),
                100
            ));
            assert_eq!(contract.balance_of(AccountId::from([0x0; 32])), 50);
            assert_eq!(
                contract.allowance(AccountId::from([0x1; 32]), AccountId::from([0x1; 32])),
                150
            );
        }
    }
}

测试：

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cargo test
#或
cargo +nightly test

编译：

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cargo contract build
#或
cargo +nightly contract build

编译好后的合约在target目录中erc20/target/ink/，其中包含一个erc20.wasm和erc20.contract文件。.contract文件就是用来部署到链上的合约文件，而wasm文件则包含合约的ABI。

启动节点：

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substrate-contracts-node --dev

rococo测试网app环境（平行链）
领取该合约平行链的token：前往Rococo faucet matrix channel 在频道里输入：

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!drip 你的Substrate地址（即SS58 prefix的地址 ）:1002

打开合约用户界面 连接节点，也可以去polkadot-app提供的合约页面(建议，功能齐全)
单击“添加新合同”。
单击上传新合约代码，即上传前面生成的erc20.contract文件

具体页面上合约的调用比较简单，这里就不详细阐述了

备注：
phala提供了一个合约测试环境也很方便：
phala合约测试
可以在此处领取phala的测试币：
phala测试币领取方式一
phala测试币领取方式二 手动将内置账户余额转入到你的测试账号

总结

本文编辑完毕

参考

[1] Substrate官方文档

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