React Day Picker 仅在第二次单击时更改“to”状态

Question

所有...我正在使用“react-day-picker”组件通过两个输入来选择日期范围。

我开始逐字使用此页面上的示例：http://react-day-picker.js.org/examples/input-from-to。我所做的唯一更改是将console.log(this.state) 添加到handleFromChange 和handleToChange 方法。

该组件乍一看似乎可以工作，但是当我 console.log 状态时，我发现“to”状态仅在 second 次选择“to”日期时更新在选择器中。第一次选择“到”日期会返回“未定义”。

看看这段代码，有没有什么不正确的地方跳出来？同样，此代码由组件的创建者提供。我试图弄清楚它是组件的错误、示例代码的错误还是其他问题。

谢谢！

为方便起见，这是我正在使用的代码：

import React from 'react';
import moment from 'moment';
import Helmet from 'react-helmet';

import DayPickerInput from 'react-day-picker/DayPickerInput';
import 'react-day-picker/lib/style.css';

import { formatDate, parseDate } from 'react-day-picker/moment';

export default class Example extends React.Component {
  constructor(props) {
    super(props);
    this.handleFromChange = this.handleFromChange.bind(this);
    this.handleToChange = this.handleToChange.bind(this);
    this.state = {
      from: undefined,
      to: undefined,
    };
  }
  componentWillUnmount() {
    clearTimeout(this.timeout);
  }
  focusTo() {
    // Focus to `to` field. A timeout is required here because the overlays
    // already set timeouts to work well with input fields
    this.timeout = setTimeout(() => this.to.getInput().focus(), 0);
  }
  showFromMonth() {
    const { from, to } = this.state;
    if (!from) {
      return;
    }
    if (moment(to).diff(moment(from), 'months') < 2) {
      this.to.getDayPicker().showMonth(from);
    }
  }
  handleFromChange(from) {
    // Change the from date and focus the "to" input field
    this.setState({ from }, () => {
      if (!this.state.to) {
        this.focusTo();
      }
    });
  }
  handleToChange(to) {
    this.setState({ to }, this.showFromMonth);
  }
  render() {
    const { from, to } = this.state;
    const modifiers = { start: from, end: to };
    return (
      <div className="InputFromTo">
        <DayPickerInput
          value={from}
          placeholder="From"
          format="LL"
          formatDate={formatDate}
          parseDate={parseDate}
          dayPickerProps={{
            selectedDays: [from, { from, to }],
            disabledDays: { after: to },
            toMonth: to,
            modifiers,
            numberOfMonths: 2,
          }}
          onDayChange={this.handleFromChange}
        />{' '}
        —{' '}
        <span className="InputFromTo-to">
          <DayPickerInput
            ref={el => (this.to = el)}
            value={to}
            placeholder="To"
            format="LL"
            formatDate={formatDate}
            parseDate={parseDate}
            dayPickerProps={{
              selectedDays: [from, { from, to }],
              disabledDays: { before: from },
              modifiers,
              month: from,
              fromMonth: from,
              numberOfMonths: 2,
            }}
            onDayChange={this.handleToChange}
          />
        </span>
        <Helmet>
          <style>{`
  .InputFromTo .DayPicker-Day--selected:not(.DayPicker-Day--start):not(.DayPicker-Day--end):not(.DayPicker-Day--outside) {
    background-color: #f0f8ff !important;
    color: #4a90e2;
  }
  .InputFromTo .DayPicker-Day {
    border-radius: 0 !important;
  }
  .InputFromTo .DayPicker-Day--start {
    border-top-left-radius: 50% !important;
    border-bottom-left-radius: 50% !important;
  }
  .InputFromTo .DayPicker-Day--end {
    border-top-right-radius: 50% !important;
    border-bottom-right-radius: 50% !important;
  }
  .InputFromTo .DayPickerInput-Overlay {
    width: 550px;
  }
  .InputFromTo-to .DayPickerInput-Overlay {
    margin-left: -198px;
  }
`}</style>
        </Helmet>
      </div>
    );
  }
}

Answer 1

我检查了你的代码。看起来它在状态中为 To 和 From 两个值都收到了适当的值。也许你在错误的地方有 console.log(this.state) 。

让我告诉你，setState 方法是异步的，所以你一定得到了错误的值。

我已在适当的状态下添加了一个 console.log 语句，以向您显示该值已正确反映。看看下面的代码

import React from 'react';
import moment from 'moment';
import Helmet from 'react-helmet';

import DayPickerInput from 'react-day-picker/DayPickerInput';
import 'react-day-picker/lib/style.css';

import { formatDate, parseDate } from 'react-day-picker/moment';

export default class Example extends React.Component {
    constructor(props) {
        super(props);
        this.handleFromChange = this.handleFromChange.bind(this);
        this.handleToChange = this.handleToChange.bind(this);
        this.state = {
            from: undefined,
            to: undefined,
        };
    }
    componentWillUnmount() {
        clearTimeout(this.timeout);
    }
    focusTo() {
        // Focus to `to` field. A timeout is required here because the overlays
        // already set timeouts to work well with input fields
        this.timeout = setTimeout(() => this.to.getInput().focus(), 0);
    }
    showFromMonth() {
        console.log("value from the state",this.state);
        const { from, to } = this.state;
        if (!from) {
            return;
        }
        if (moment(to).diff(moment(from), 'months') < 2) {
            this.to.getDayPicker().showMonth(from);
        }
    }
    handleFromChange(from) {
        console.log("New From value", from);
        // Change the from date and focus the "to" input field
        this.setState({ from }, () => {
            console.log("value from the state",this.state);
            if (!this.state.to) {
                this.focusTo();
            }
        });
    }
    handleToChange(to) {
        console.log("New To value", to);
        this.setState({ to }, this.showFromMonth);
    }
    render() {
        const { from, to } = this.state;
        const modifiers = { start: from, end: to };
        return (
            <div className="InputFromTo">
                <DayPickerInput
                    value={from}
                    placeholder="From"
                    format="LL"
                    formatDate={formatDate}
                    parseDate={parseDate}
                    dayPickerProps={{
                        selectedDays: [from, { from, to }],
                        disabledDays: { after: to },
                        toMonth: to,
                        modifiers,
                        numberOfMonths: 2,
                    }}
                    onDayChange={this.handleFromChange}
                />{' '}
                —{' '}
                <span className="InputFromTo-to">
          <DayPickerInput
              ref={el => (this.to = el)}
              value={to}
              placeholder="To"
              format="LL"
              formatDate={formatDate}
              parseDate={parseDate}
              dayPickerProps={{
                  selectedDays: [from, { from, to }],
                  disabledDays: { before: from },
                  modifiers,
                  month: from,
                  fromMonth: from,
                  numberOfMonths: 2,
              }}
              onDayChange={this.handleToChange}
          />
        </span>
                <Helmet>
                    <style>{`
  .InputFromTo .DayPicker-Day--selected:not(.DayPicker-Day--start):not(.DayPicker-Day--end):not(.DayPicker-Day--outside) {
    background-color: #f0f8ff !important;
    color: #4a90e2;
  }
  .InputFromTo .DayPicker-Day {
    border-radius: 0 !important;
  }
  .InputFromTo .DayPicker-Day--start {
    border-top-left-radius: 50% !important;
    border-bottom-left-radius: 50% !important;
  }
  .InputFromTo .DayPicker-Day--end {
    border-top-right-radius: 50% !important;
    border-bottom-right-radius: 50% !important;
  }
  .InputFromTo .DayPickerInput-Overlay {
    width: 550px;
  }
  .InputFromTo-to .DayPickerInput-Overlay {
    margin-left: -198px;
  }
`}</style>
                </Helmet>
            </div>
        );
    }
}