一个组件正在将文本类型的不受控制的输入更改为 ReactJS 中的受控错误

A component is changing an uncontrolled input of type text to be controlled error in ReactJS(一个组件正在将文本类型的不受控制的输入更改为 ReactJS 中的受控错误)

问题描述

警告:组件正在更改要控制的文本类型的不受控制的输入.输入元素不应从不受控切换到受控(反之亦然).在组件的生命周期内决定使用受控输入元素还是不受控输入元素.*

Warning: A component is changing an uncontrolled input of type text to be controlled. Input elements should not switch from uncontrolled to controlled (or vice versa). Decide between using a controlled or uncontrolled input element for the lifetime of the component.*

以下是我的代码:

constructor(props) {
  super(props);
  this.state = {
    fields: {},
    errors: {}
  }
  this.onSubmit = this.onSubmit.bind(this);
}

....

onChange(field, e){
  let fields = this.state.fields;
  fields[field] = e.target.value;
  this.setState({fields});
}

....

render() {
  return(
    <div className="form-group">
      <input
        value={this.state.fields["name"]}
        onChange={this.onChange.bind(this, "name")}
        className="form-control"
        type="text"
        refs="name"
        placeholder="Name *"
      />
      <span style={{color: "red"}}>{this.state.errors["name"]}</span>
    </div>
  )
}

推荐答案

原因是，在你定义的状态下:

The reason is, in state you defined:

this.state = { fields: {} }

fields 作为一个空白对象，所以在第一次渲染时，this.state.fields.name 将是 undefined，并且输入字段将得到它的值:

fields as a blank object, so during the first rendering this.state.fields.name will be undefined, and the input field will get its value as:

value={undefined}

因此，输入字段将变得不受控制.

Because of that, the input field will become uncontrolled.

在输入中输入任何值后，状态中的 fields 将更改为:

Once you enter any value in input, fields in state gets changed to:

this.state = { fields: {name: 'xyz'} }

此时输入字段被转换为受控组件；这就是您收到错误的原因:

And at that time the input field gets converted into a controlled component; that's why you are getting the error:

组件正在将文本类型的不受控制的输入更改为控制.

A component is changing an uncontrolled input of type text to be controlled.

可能的解决方案:

1- 将状态中的 fields 定义为:

1- Define the fields in state as:

this.state = { fields: {name: ''} }

2- 或者使用 短路评估像这样:

2- Or define the value property by using Short-circuit evaluation like this:

value={this.state.fields.name || ''}   // (undefined || '') = ''

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