Class properties must be methods. Expected '(' but instead saw '='

Question

I have a react app, and I have this code, but it looks like the fetchdata m ethod is full of syntax errors, the first one shown on the title of the question.

Whats wrong with the method?

import React, { Component } from 'react';

import { Row, Col } from 'antd';
import PageHeader from '../../components/utility/pageHeader';
import Box from '../../components/utility/box';
import LayoutWrapper from '../../components/utility/layoutWrapper.js';
import ContentHolder from '../../components/utility/contentHolder';
import basicStyle from '../../settings/basicStyle';
import IntlMessages from '../../components/utility/intlMessages';
import { adalApiFetch } from '../../adalConfig';

const data = {
  TenantId: this.this.state.tenantid,
  TenanrUrl: this.state.tenanturl,
  TenantPassword: this.state.tenantpassword 
};

const options = {
  method: 'post',
  data: data,
  config: {
    headers: {
      'Content-Type': 'multipart/form-data'
    }
  }
};

export default class extends Component {
  constructor(props) {
    super(props);
    this.state = {value: ''};
    this.handleChangeTenantUrl = this.handleChangeTenantUrl.bind(this);
    this.handleChangeTenantPassword = this.handleChangeTenantPassword.bind(this);
    this.handleChangeTenantId= this.handleChangeTenantId.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleChangeTenantUrl(event){
    this.setState({tenanturl: event.target.value});
  }

  handleChangeTenantPassword(event){
    this.setState({tenantpassword: event.target.value});
  }

  handleChangeTenantId(event){
    this.setState({tenantid: event.target.value});
  }

  handleSubmit(event){
    alert('A name was submitted: ' + this.state.value);
    event.preventDefault();
    fetchData();
  }

  fetchData = () => {
    adalApiFetch(fetch, "/tenant", options)
      .then(response => response.json())
      .then(responseJson => {
        if (!this.isCancelled) {
          this.setState({ data: responseJson });
        }
      })
      .catch(error => {
        console.error(error);
      });
  };

  upload(e) {

      let data = new FormData();

      //Append files to form data
      let files = e.target.files;
      for (let i = 0; i < files.length; i++) {
        data.append('files', files[i], files[i].name);
      }

      let d = {
        method: 'post',
        url: API_SERVER,
        data: data,
        config: {
          headers: {
            'Content-Type': 'multipart/form-data'
          },
        },
        onUploadProgress: (eve) => {
          let progress = utility.UploadProgress(eve);
          if (progress == 100) {
            console.log("Done");
          } else {
            console.log("Uploading...",progress);
          }
        },
      };
      let req = axios(d);

      return new Promise((resolve)=>{
          req.then((res)=>{
              return resolve(res.data);
          });
      });

  }

  render(){
    const { data } = this.state;
    const { rowStyle, colStyle, gutter } = basicStyle;

    return (
      <div>
        <LayoutWrapper>
        <PageHeader>{<IntlMessages id="pageTitles.TenantAdministration" />}</PageHeader>
        <Row style={rowStyle} gutter={gutter} justify="start">
          <Col md={12} sm={12} xs={24} style={colStyle}>
            <Box
              title={<IntlMessages id="pageTitles.TenantAdministration" />}
              subtitle={<IntlMessages id="pageTitles.TenantAdministration" />}
            >
              <ContentHolder>
              <form onSubmit={this.handleSubmit}>
                <label>
                  TenantId:
                  <input type="text" value={this.state.tenantid} onChange={this.handleChangeTenantId} />
                </label>
                <label>
                  TenantUrl:
                  <input type="text" value={this.state.tenanturl} onChange={this.handleChangeTenantUrl} />
                </label>
                <label>
                  TenantPassword:
                  <input type="text" value={this.state.tenantpassword} onChange={this.handleChangeTenantPassword} />
                </label>
                <label>
                  Certificate:
                  <input onChange = { e => this.upload(e) } type = "file" id = "files" ref = { file => this.fileUpload } />
                 </label>             
              <input type="submit" value="Submit" />
              </form>
              </ContentHolder>
            </Box>
          </Col>
        </Row>
      </LayoutWrapper>
      </div>
    );
  }
}

Answer 1

You have written your fetchData method in the form of a class field which is not part of the language yet. You could add the Babel plugin proposal-class-properties or a preset that has it, like the stage 2 preset. (Note that the class field proposal is a finished stage 4 proposal as of April 2021.)

If you don't want to configure Babel, you could bind the method in your constructor instead, like you have done with your other methods:

export default class extends Component {
  constructor(props) {
    super(props);
    this.state = {value: ''};
    this.handleChangeTenantUrl = this.handleChangeTenantUrl.bind(this);
    this.handleChangeTenantPassword = this.handleChangeTenantPassword.bind(this);
    this.handleChangeTenantId= this.handleChangeTenantId.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
    this.fetchData = this.fetchData.bind(this);
  }

  fetchData() {
    adalApiFetch(fetch, "/tenant", options)
      .then(response => response.json())
      .then(responseJson => {
        if (!this.isCancelled) {
          this.setState({ data: responseJson });
        }
      })
      .catch(error => {
        console.error(error);
      });
  }

  // ...
}

Answer 2

Have you defined the fetchdata variable previously?If not, perhaps you should do it in the current line:

var fetchdata = () => { ...