[Near Protocol] Near开发Demo浅析-Gamble Game Near（二）：Dapp

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

Dapp

接着上一期继续分享

源代码在Github上可以找到，以下是Dapp链接：

https://github.com/Yang94J/Gamble_Game_Near_Front

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简介

本项目依托Vue，搭建前端应用，调用near-api-js与部署好的合约进行交互，完成掷骰子功能。

环境搭建

• Prerequisite : 系统中应当已经安装好Nodejs，Vue3

• 项目搭建：

    vue create gamble_gamble_near_front

  最终代码框架如下：
  
  主要对/components/GambleGame.vue、App.vue、config.js、main.js、store.js、.env、package.json及vue.config.js进行介绍。

代码解析

package.json

以下是package.json重点部分

  "dependencies": {
    "@rollup/plugin-inject": "^4.0.4",
    "buffer": "^6.0.3",
    "core-js": "^3.8.3",
    "near-api-js": "^0.44.2",
    "vue": "^3.2.13",
    "vuex": "^4.0.2"
  },

此处指明了对buffer、near-api-js、vue、vuex等依赖（尤其是buffer，必须要引入并显式声明，否则工程会出现类似Can't find variable: Buffer之类的错误）

.env

VUE_APP_CONTRACT_NAME=gamble_game1.XXX.testnet

指明dapp所需调用的合约名称（测试网）

main.js

import { createApp } from 'vue'
import App from './App.vue'
import store from './store'

import { Buffer } from "buffer"; 
global.Buffer = Buffer;

createApp(App).use(store).mount('#app')

请注意此处显式声明了global.Buffer

config.js

const CONTRACT_NAME = process.env.VUE_APP_CONTRACT_NAME;

从.env文件中读取合约名称

case 'testnet':
      return {
        networkId: 'testnet',
        nodeUrl: 'https://rpc.testnet.near.org',
        contractName: CONTRACT_NAME,
        walletUrl: 'https://wallet.testnet.near.org',
        helperUrl: 'https://helper.testnet.near.org',
        explorerUrl: 'https://explorer.testnet.near.org',
      };

根据用户输入环境，选择对应的网络配置（此处为测试网）。

store.js

store.js存储数据到本地浏览器，获取缓存等，可以参考该链接

state: {
    contract: null,
    currentUser: null,
    wallet: null,
    nearConfig: null
  },

存储状态包括合约、当前用户、钱包和near配置

  mutations: {
    setupNear(state, payload) {
      state.contract = payload.contract;
      state.currentUser = payload.currentUser;
      state.wallet = payload.wallet;
      state.nearConfig = payload.nearConfig;
    }
  }

设置state对象

 async initNear({ commit }) {
      const nearConfig = getConfigurations('testnet');

      const near = await nearApi.connect({
        deps: {
          keyStore: new nearApi.keyStores.BrowserLocalStorageKeyStore()
        },
        ...nearConfig
      });

      const wallet = new nearApi.WalletConnection(near);
      console.log(wallet)

      let currentUser;

      if (wallet.getAccountId()) {
        currentUser = {
          accountId: wallet.getAccountId(),
          balance: (await wallet.account().state()).amount,
          balanceInNear : (await wallet.account().state()).amount / (10 ** 24),
        }
      }

      console.log(currentUser)

      const contract = await new nearApi.Contract(wallet.account(), process.env.VUE_APP_CONTRACT_NAME || 'gamble_game1.young_cn.testnet', {
        viewMethods: ['get_maximum_gamble_price'],
        changeMethods: ['gamble','sponsor'],
        sender: wallet.getAccountId()
      });
      console.log(contract);
      // Commit and send to mutation.
      commit('setupNear', { contract, currentUser, wallet, nearConfig });
    }
  }

此处initNear函数获取测试网配置，生成合约、钱包信息（需要用户登录）、用户信息等。

GambleGame.vue

    

        
Dice Gamble game
        
          {{ currentUser ? 'Log Out' : 'Log In' }}
        
    

根据当前用户情况，生成登入登出按钮

 
Hi, {{currentUser.accountId}}, your balance is {{currentUser.balanceInNear}} Near

显示当前用户id，当前余额（CurrentUser信息参见store.js）

    

        Maximum : {{gambleLimit}} Near 
         Refresh
     

显示当前最大投注量，通过refresh函数访问智能合约刷新最大投注量

      

        Gamble:
        
        Gamble
      

投注按钮，调用gamblegame方法进行投注

      

        Sponsor:
        
        Sponsor us
      

赞助按钮，调用sponsorus方法进行赞助

  async created(){
    console.log("created")
    console.log(sessionStorage.getItem('gambleLimit'))
    if (sessionStorage.getItem('gambleLimit')) {
      this.gambleLimit = sessionStorage.getItem('gambleLimit')
    }
  },

用created钩子函数来自动获取最大投注量（否则数据将丢失）

  async mounted() {
    var that  = this
      console.log("Mount")
      setInterval(
        () => {
          console.log("refresh")
          that.refresh()
          },3000
      )
  },

使用mounted钩子函数来设置自动更新最大投注量-考虑合约的并发。

signIn() {
      this.wallet.requestSignIn(
        this.nearConfig.contractName,
        'Near Gamble Game'
      );
    },
    signOut() {
      this.wallet.signOut();
      window.location.replace(window.location.origin + window.location.pathname)
    },

signIn和signOut方法调用near.api.js实现与钱包的交互

    async gamblegame(){
      try{
        await this.contract.gamble(
          {},
          this.gas,
          Big(this.gamble).times(10**24).toFixed()
        );
      }catch (e) {
        console.log(e);
      }
    },
    async sponsorus(){
      try{
        await this.contract.sponsor(
          {},
          this.gas,
          Big(this.sponsor).times(10**24).toFixed()
        );
      }catch (e) {
        console.log(e);
        alert('Something went wrong! Check the console.');
      }
    },
    async refresh(){
      this.gambleLimit = await this.contract.get_maximum_gamble_price()
      this.gambleLimit = this.gambleLimit / (10 ** 24)
      sessionStorage.setItem('gambleLimit',this.gambleLimit)
    }
  }

gambleGame、sponsorus和refresh都是异步方法。具体contract方法信息在store.js里通过以下进行声明：

        viewMethods: ['get_maximum_gamble_price'],
        changeMethods: ['gamble','sponsor'],

部署

• vue.config.js修改其配置如下：

const { defineConfig } = require('@vue/cli-service')
module.exports = defineConfig({
  transpileDependencies: true,
  publicPath:'./',
})

将路径改为相对路径

• 构建

        npm run build

• 运行

    npm run serve

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效果展示

至此，Dapp部分完成。

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诚然，这个demo很明显还有很多不足的地方，但也算一个不错的开始。大家有想法也欢迎和我一起讨论。互相交流，共同进步。