问未捕获的长度:无法使用react和redux-TypeError验证读取未定义的属性'length‘
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Stack Overflow用户

提问于 2017-05-31 20:08:23

回答 3查看 10.4K关注 0票数 2

我在这里使用redux-form和react，并尝试使用验证。我已经做好了所有的工作，但是由于某些原因，当我尝试验证一个字段必须是某个长度属性时，我得到了：

Uncaught TypeError: Cannot read property 'length' of undefined

代码如下：

import React, { Component } from 'react';
import {Field, reduxForm} from 'redux-form';

class PostsNew extends Component {
  constructor(props) {
    super(props);

    this.onSubmit = this.onSubmit.bind(this);
  }

  renderField(field) {
    return (
      <div className="form-group">
        <label><strong>{field.label}:</strong></label>
        <input
          className="form-control"
          type="text"
          {...field.input}
        />
        {field.meta.touched ? field.meta.error : ''}
      </div>
    )
  }

  onSubmit(values) {
    console.log(values);
  }

  render() {
    const { handleSubmit } = this.props;

    return (
      <form onSubmit={handleSubmit(this.onSubmit)}>
        <Field
          label="Title for Post"
          name="title"
          component={this.renderField}
        />
        <Field
          label="Categories"
          name="categories"
          component={this.renderField}
        />
        <Field
          label="Post Content"
          name="content"
          component={this.renderField}
        />
        <button type="submit" className="btn btn-success">Submit</button>
      </form>
    );
  }
}

function validate(values) {
  const errors = {};

  //Validate the inputs from values
  if(!values.title) {
    errors.title = "Enter a title!";
  }
  if(!values.categories) {
    errors.categories = "Enter some categories!";
  }

  if(!values.content) {
    errors.content = "Enter some content please!";
  }

  if(!values.content.length < 20) {
    errors.content = "Content must be longer than 3 characters!";
  }
  //If errors is empty, the form is fine to submit
  //If errors has any properties, redux form assumes form is invalid
  return errors;
}

export default reduxForm({
  validate,
  form: 'PostsNewForm'
})(PostsNew);

javascript

reactjs

redux

redux-form

回答 3

Stack Overflow用户

发布于 2017-05-31 20:55:55

if(!values.content || !values.content.length < 20){ }

您也可以先检查对象，然后再检查属性本身。

票数 3

Stack Overflow用户

发布于 2017-05-31 21:06:50

我不确定这是否是正确的方法，但它确实有效！

if(values.content){
    if(values.content.length < 20){
      errors.content = "Content must be longer than 20 characters!";
    }
  }

票数 1

Stack Overflow用户

发布于 2018-10-25 09:55:47

我觉得最好的方法是做内联验证，这样

<Field
  label="Post Content"
  name="content"
  component={this.renderField}
  validate={(value) => value && value.length > 20 ? undefined : 'Content must be longer than 20 characters!'}
/>