class 组件默认导出 function

Question

嗨，我需要帮助将此 class 组件迁移到默认导出 function，因为我的代码在默认导出 function 中，我需要帮助才能将其传递为 i 格式

import React, { Component } from "react";

export default class SingleImageUploadComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      file: null
    };
    this.uploadSingleFile = this.uploadSingleFile.bind(this);
    this.upload = this.upload.bind(this);
  }

  uploadSingleFile(e) {
    this.setState({
      file: URL.createObjectURL(e.target.files[0])
    });
  }

  upload(e) {
    e.preventDefault();
    console.log(this.state.file);
  }

  render() {
    let imgPreview;
    if (this.state.file) {
      imgPreview = <img src={this.state.file} alt="" />;
    }
    return (
      <form>
        <div className="form-group preview">{imgPreview}</div>

        <div className="form-group">
          <input
            type="file"
            className="form-control"
            onChange={this.uploadSingleFile}
          />
        </div>
        <button
          type="button"
          className="btn btn-primary btn-block"
          onClick={this.upload}
        >
          Upload
        </button>
      </form>
    );
  }
}

https://codesandbox.io/s/pedantic-brattain-irypt?file=/src/App.js

Answer 1

import React, { useState } from "react";

const SingleImageUploadComponent = () => {
  const [file, setFile] = useState(null);

  function uploadSingleFile(e) {
    setFile(URL.createObjectURL(e.target.files[0]));
    console.log("file", file);
  }

  function upload(e) {
    e.preventDefault();
    console.log(file);
  }

  return (
    <form>
      <div className="form-group preview">
        {file && <img src={file} alt="" />}
      </div>

      <div className="form-group">
        <input
          type="file"
          className="form-control"
          onChange={uploadSingleFile}
        />
      </div>
      <button
        type="button"
        className="btn btn-primary btn-block"
        onClick={upload}
      >
        Upload
      </button>
    </form>
  );
};

export default SingleImageUploadComponent;

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