关于区块链:Near-Protocol-Near开发Demo浅析Gamble-Game-Near一智能合约

[Near Protocol] Near开发Demo浅析-Gamble Game Near

智能合约

大家好，Near Protocol是近年来比拟引人注目的公链我的项目，其分片技术也使得其性能和稳定性呈现了很大的晋升和冲破。我最近对Near相干开发的根底概念进行了学习，以掷色子游戏的概念为根底，开发了Near 合约+Dapp的Demo，当初和大家分享探讨，心愿都能有所进益。

源代码在Github上能够找到，以下是智能合约链接：

https://github.com/Yang94J/Gamble_Game_Near

简介

合约名称：Gamble
合约性能：容许用户通过发送Near进行投注，通过随机数模仿掷色子流动，当掷到6时，能够取得6倍返还。
实现语言：Rust
部署网络： Near Testnet
Near-sdk文档：https://www.near-sdk.io

环境搭建

Prerequisite : 零碎中该当曾经装置好Rust

装置wasm32（编译）：

      rustup target add wasm32-unknown-unknown

初始化我的项目（编译）：
```
      cargo new Gamble_Game_Near
```
在生成的工程上进行目录的批改，最终构造如下：

其中lib.rs是合约文件，而Cargo.toml形容依赖（你能够了解为相似于Maven我的项目中的pom.xml），而Cargo.lock则蕴含依赖项的确切信息。

Cargo.toml

以下是Cargo.toml重点局部

[lib]crate-type = ["cdylib","rlib"][dependencies]uint = {version = "0.9.0", default-features = false}near-sdk = "4.0.0-pre.7"near-contract-standards = "4.0.0-pre.7"

其中crate-type指定为C动态链接库及Rust链接库，依赖应用4.0.0-pre.7版本的near-sdk

lib.rs

lib.rs首先从near-sdk中导入相干函数及接口：

use near_sdk::{    borsh::{self, BorshDeserialize, BorshSerialize},    near_bindgen, Balance,PanicOnDefault,    env, require, log,  Promise, };

同时通过#[near_bindgen]和#[derive(BorshDeserialize, BorshSerialize,PanicOnDefault)]来申明Gamble类为智能合约类。#[near_bindgen]宏用以生成Near合约所需的代码并对外裸露接口。#[derive(BorshDeserialize, BorshSerialize,PanicOnDefault)]则声明序列化、反序列化，且要求实现构造函数。Gamble类中蕴含gamble_min_price和gamble_max_price属性，为投注的最小值和最大值。

pub struct Gamble {    // Minimum price that should be transfered to the contract, revert otherwise    gamble_min_price : Balance,    // Maximum price that should be transfered to the contract, revert otherwise    gamble_max_price : Balance,}

本文后续实现Gamble类的相干办法，（留神&self 和 &mut self的区别，相似于solidity view和change的区别）如下：

pub fn new() -> Self ：用以初始化合约，设置gamble_min_price和gamble_max_price属性。

    #[init]    pub fn new() -> Self {                let account_balance = env::account_balance();        let gamble_max_price = account_balance / (5 * FACTOR);        log!("we have {} uints in total, be sure not to exceed the max gamble price limit {} to get {}X \n", account_balance, gamble_max_price, FACTOR);        Self{            gamble_max_price : gamble_max_price,            gamble_min_price : 0,        }    }

pub fn get_minimal_gamble_price(&self) -> u128 ：获取最小投注数量（ yoctoNEAR）

    // Get the Minimum amount of near to be transfered(Used for dapp, but usually won't as it's 0 all the time)    pub fn get_minimal_gamble_price(&self) -> u128 {        self.gamble_min_price    }

pub fn get_maximum_gamble_price(&self) -> u128：获取最大投注数量（ yoctoNEAR）

    // Get the Minimum amount of near to be transfered(Used for dapp)    pub fn get_maximum_gamble_price(&self) -> u128 {        self.gamble_max_price    }

pub fn get_balance(&self) -> u128：获取合约余额（ yoctoNEAR）

    // Get contract balance U128    pub fn get_balance(&self) -> u128 {        env::account_balance()    }

pub fn update_price(&mut self) ：更新投注最大值和最小值

    // Update price everytime the account balance changes    // Only contract call    fn update_price(&mut self){        let account_balance = env::account_balance();        self.gamble_max_price = account_balance / (5 * FACTOR);        log!("we have {} uints in total, be sure not to exceed the max gamble price limit {} to get {}X \n", account_balance, self.gamble_max_price, FACTOR);    }

pub fn sponsor(&mut self)：资助函数，即用户向合约账号发送near（ yoctoNEAR），最初更新投注下限和上限

    // The user could sponsor the contract(maybe only the owner will...)    #[payable]    pub fn sponsor(&mut self){        let sponsor_id = env::signer_account_id();        let deposit = env::attached_deposit();        log!("sponsor {} has add {} to the game to increase balance, thank you ~ \n", sponsor_id, deposit);        self.update_price();    }

pub fn gamble(&mut self) -> u8：投掷函数，返回投掷出的点数（1-6），最初更新投注下限和上限

    // The user could transfer near to get a chance to gamble    // return the dice throwed by the user (Randomly generated)    #[payable]    pub fn gamble(&mut self) -> u8{        let gambler_id = env::signer_account_id();        let deposit = env::attached_deposit();        require!(deposit>=self.gamble_min_price,"The gamble price must exceed gamble_min_price");        require!(deposit<=self.gamble_max_price,"The gamble price must not exceed gamble_max_price");                let num = self.rand_dice();        if num == FACTOR as u8 {            let amount = (deposit as f32 ) *(FACTOR as f32) * TAX;            let amount_u128 = amount  as u128;            log!("Congratuations to {}, he has won the gamble, the prize is {} \n",gambler_id,deposit);            Promise::new(gambler_id).transfer(amount_u128);        }        self.update_price();        return num;    }

pub fn rand_dice(&self) -> u8 ：基于random_seed()，生成随机数并通过取余映射到1-6

    // Generate random number from 1 to 6    pub fn rand_dice(&self) -> u8 {        *env::random_seed().get(0).unwrap()%6+1    }

后续则是单元测试局部，通过fn get_context(input: Vec<u8>) -> VMContext设置了测试背景，由fn rand_test()测试了随机数生成，fn gamble_test()则测试了合约初始化后的变量状况。

合约部署

在此之前请先装置Near-cli
编译生成

        cargo build --target wasm32-unknown-unknown --release

部署（学生成子账号再部署）

        near create-account gamble_game1.XXX.testnet --masterAccount XXX.testnet --initialBalance 100        near deploy --wasmFile target/wasm32-unknown-unknown/release/gamble_game_near.wasm --accountId gamble_game1.XXX.testnet

测试

        near call gamble_game1.XXX.testnet new  --accountId gamble_game1.XXX.testnet        near view gamble_game1.XXX.testnet get_balance        near view gamble_game1.XXX.testnet get_maximum_gamble_price        near call gamble_game1.XXX.testnet sponsor --deposit 1  --accountId XXX.testnet        near call gamble_game1.XXX.testnet gamble --deposit 1  --accountId XXX.testnet

至此，智能合约局部实现，后续会带来
[Near Protocol] Near开发Demo浅析-Gamble Game Near（二）：Dapp局部的介绍。