无法调用智能合约中的函数答案

【问题标题】：cannot call the function in smart contract无法调用智能合约中的函数
【发布时间】：2020-04-08 05:40:03
【问题描述】：

我正在尝试通过 Angular 应用程序调用 Solidity 智能合约中的方法。但我无法调用该方法。有人可以帮帮我吗。这是我在控制台中遇到的错误

TypeError: this.contract.methods.hello is not a function
at CertificateContractService.<anonymous> (certificate-contract.service.ts:32)
at Generator.next (<anonymous>)
at fulfilled (tslib.es6.js:70)
at ZoneDelegate.invoke (zone-evergreen.js:359)
at Object.onInvoke (core.js:39699)
at ZoneDelegate.invoke (zone-evergreen.js:358)
at Zone.run (zone-evergreen.js:124)
at zone-evergreen.js:855
at ZoneDelegate.invokeTask (zone-evergreen.js:391)
at Object.onInvokeTask (core.js:39680)

智能合约


contract CertificateList {

    function hello() external pure returns (string memory )  {
        return "Hello";
    }

}

角度服务

import Web3 from 'web3';
import {WEB3} from './WEB3';

declare let require: any;
declare let window: any;


@Injectable({
  providedIn: 'root'
})
export class CertificateContractService {
  private abi: any;
  private address = '0xb0fFD3498B219ad2A62Eb98fEDE591265b3C3B67';
  private contract;
  private accounts: string[];

  constructor(@Inject(WEB3) private web3: Web3) {
    this.init().then(res => {
    }).catch(err => {
      console.error(err);
    });
  }

  private async init() {
    this.abi = require('../assets/abi/CertificateList.json');
    // await this.web3.currentProvider.enable();
    this.accounts = await this.web3.eth.getAccounts();

    this.contract = new this.web3.eth.Contract(this.abi, this.address, {gas: 1000000, gasPrice: '10000000000000'});

    this.contract.methods.hello().send()
      .then(receipt => {
        console.log(receipt);
      }).catch(err => {
      console.error(err);
    });
  }
}

提供者

import { InjectionToken } from '@angular/core';
import Web3 from 'web3';

export const WEB3 = new InjectionToken<Web3>('web3', {
  providedIn: 'root',
  factory: () => {
    try {
      window['ethereum'].autoRefreshOnNetworkChange = false;
      const provider = ('ethereum' in window) ? window['ethereum'] : Web3['givenProvider'];
      return new Web3(provider);
    } catch (err) {
      throw new Error('Non-Ethereum browser detected. You should consider trying Mist or MetaMask!');
    }
  }
});

【问题讨论】：

标签： blockchain solidity truffle

【解决方案1】：

确保 ../assets/abi/CertificateList.json 仅包含有效的 abi。如果是直接执行truffle compile或solc CertificateList.sol获取到这个文件，需要从json文件中提取abi。

var contractJson = require('../assets/abi/CertificateList.json');
this.abi = contractJson['abi'];

另外，你不能在纯函数上使用methods.hello.send。 send 方法只能在修改合约状态的函数上调用，即 payable 或 unspecified 函数。要调用 pure 或 view 函数，应使用call 方法。如需更多信息，请参阅web3.eth.Contract。

this.contract.methods.hello().call()
  .then(receipt => {
    console.log(receipt);
  }).catch(err => {
  console.error(err);
});

【讨论】：