react+ts 实现类组件 父子组件传值

父传子

父组件Login
父组件Login 定义了一个参数叫callBack对应的函数(codeCallBackHanderl)传给子组件,子组件通过props调用,
import RandomImgCode from "@/components/RandomImgCode";

 
 
 // 子组件传回的方法
codeCallBackHanderl = (value:string) => {
    this.setState({
      imgCode:value
    })
    console.log(value,'父组件接受的value')
  }

子组件RandomImgCode
import React, { Component } from 'react';
import { RandomImgCodeInterface } from '@/assets/Interface';
class RandomImgCode extends Component{
  state = {
    code: '',
      codeLength: 4,
      fontSizeMin: 20,
      fontSizeMax: 22,
      backgroundColorMin: 240,
      backgroundColorMax: 250,
      colorMin: 10,
      colorMax: 20,
      lineColorMin: 40,
      lineColorMax: 180,
      contentWidth: 120,
      contentHeight: 38,
      showError: false, // 默认不显示验证码的错误信息
  }
  canvas:any
  componentDidMount() {
    this.canvas = React.createRef()
    this.randomCode()
  }
  // 生成随机数
  randomNum = (min:any, max:any) => {
    return Math.floor(Math.random() * (max - min) + min)
  }
  // 生成随机颜色
  randomColor(min:any, max:any) {
    const r = this.randomNum(min, max)
    const g = this.randomNum(min, max)
    const b = this.randomNum(min, max)
    return `rgb(${r}, ${g}, ${b})`
  }
  drawText(ctx:any, txt:any, i:any) {
    ctx.fillStyle = this.randomColor(this.state.colorMin, this.state.colorMax)
    const fontSize = this.randomNum(this.state.fontSizeMin, this.state.fontSizeMax)
    ctx.font = fontSize + 'px SimHei'
    const padding = 10;
    const offset = (this.state.contentWidth - 40) / (this.state.code.length - 1)
    let x = padding;
    if (i > 0) {
        x = padding + (i * offset)
    }
    let y = this.randomNum(this.state.fontSizeMax, this.state.contentHeight - 5)
    if (fontSize > 40) {
        y = 40
    }
    const deg = this.randomNum(-10, 10)
    // 修改坐标原点和旋转角度
    ctx.translate(x, y)
    ctx.rotate(deg * Math.PI / 180)
    ctx.fillText(txt, 0, 0)
    // 恢复坐标原点和旋转角度
    ctx.rotate(-deg * Math.PI / 180)
    ctx.translate(-x, -y)
  }
  // 绘制干扰线
  drawLine(ctx:any) {
    for (let i = 0; i < 1; i++) {
        ctx.strokeStyle = this.randomColor(this.state.lineColorMin, this.state.lineColorMax)
        ctx.beginPath()
        ctx.moveTo(this.randomNum(0, this.state.contentWidth), this.randomNum(0, this.state.contentHeight))
        ctx.lineTo(this.randomNum(0, this.state.contentWidth), this.randomNum(0, this.state.contentHeight))
        ctx.stroke()
    }
  }
  // 绘制干扰点
  drawDot(ctx:any) {
    for (let i = 0; i < 100; i++) {
        ctx.fillStyle = this.randomColor(0, 255)
        ctx.beginPath()
        ctx.arc(this.randomNum(0, this.state.contentWidth), this.randomNum(0, this.state.contentHeight), 1, 0, 2 * Math.PI)
        ctx.fill()
    }
  }
  // 图片验证码点击事件,重新生成验证码
  reloadPic = () => {
    this.randomCode()
  }
  // 随机生成验证码
  randomCode() {
    let random = ''
    // 去掉了I l i o O,可自行添加
    const str = 'QWERTYUPLKJHGFDSAZXCVBNMqwertyupkjhgfdsazxcvbnm1234567890'
    for (let i = 0; i < this.state.codeLength; i++) {
        const index = Math.floor(Math.random() * 57);
        random += str[index];
    }
    this.setState({
        code: random
    }, () => {
        const canvas = this.canvas.current;
        const ctx = canvas.getContext('2d')
        ctx.textBaseline = 'bottom'
        // 绘制背景
        ctx.fillStyle = this.randomColor(this.state.backgroundColorMin, this.state.backgroundColorMax)
        ctx.fillRect(0, 0, this.state.contentWidth, this.state.contentHeight)
        // 绘制文字
        for (let i = 0; i < this.state.code.length; i++) {
            this.drawText(ctx, this.state.code[i], i)
        }
        this.drawLine(ctx)
        this.drawDot(ctx)
        // 绘制后将图片验证码传递回父组件
        this.props.callBack(this.state.code)
    })
  }

  render(){
    return(
      

        
      
    )
  }
}


export default RandomImgCode

注意：子组件中一定要定义props类型,不然父组件传值过来会报错

父组件调用子组件的方法:
1.定义一个ref,
2.通过createRef获取ref对象
3.最后父组件点击触发子组件的reloadPic方法