通过道具传递价值从无国籍的孩子到父母 [英] Passing Values via Props From React Stateless Child to Parent

问题描述

CONTEXT

我正在尝试传递输入值字段（ conditionTitle ）从React无状态子组件（ AddConditionSelect ）添加到将保持我的状态的父组件（ AddConditionDashboard ）。

I'm trying to pass input value fields (conditionTitle) from a React Stateless child component (AddConditionSelect) to the parent component (AddConditionDashboard) that will hold my state.

PROBLEM

我遵循 React documentation ，但是它们使用的引用仅在组件有状态时才有效。我不想在子组件中设置任何状态，但仍然可以访问父级中的输入。

I followed the model shown in the React documentation, but they are using refs, which only works if the component is stateful. I do not want to have to set any state in the child component, but still be able to access the input in the parent.

在其当前形式中，我收到一条警告，无状态函数组件不能被赋予参考，导致道具为空且未定义。

In its current form, I am getting a Warning, that the stateless function components cannot be given refs, resulting in props being null and undefined.

父组件：

import AddConditionSelect from '../containers/AddConditionSelect.js';

class AddConditionDashboard extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      conditionTitle: '',
      conditionType: ''
    };
  }

  handleUserInput({conditionTitleInput}) {
    this.setState({
      conditionTitle:conditionTitle
    })

  }

  render() {
    const {error, segmentId} = this.props;

    return (
      <div>

    <AddConditionSelect segmentId={segmentId} conditionTitle={this.state.conditionTitle} onUserInput={this.handleUserInput} />


    <PanelFooter theme="default">
      <Button backgroundColor="primary" color="white" inverted={true} rounded={true} onClick={(event) => this.onSubmit(event)}>
        Next Step
      </Button>
    </PanelFooter>

      </div>
    );
  }

}

export default AddConditionDashboard;

子组件：

class AddConditionSelect extends React.Component {

  onInputChange: function() {
    this.props.onUserInput(
      this.refs.conditionTitleInput.value,
    )
  },

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

    return (
      <div>

        <Panel theme="info">

        <Divider />

        Please enter a name {error ? <Message inverted={true}  rounded={true}  theme="error">{error}</Message>  : null}
          <Input value={this.props.conditionTitle} ref="conditionTitleInput" label="" type="text" buttonLabel="Add Condition" name="add_segment" onChange={this.onInputChange} placeholder="Condition Title"/>

       </Panel>
     </div>
    );
  }

}
export default AddConditionSelect;

推荐答案

如何将事件处理程序直接传递给<输入> ？这样你就可以将更改事件直接传递给您的父级（< Input> 的祖父母），您可以从 event.target中提取值。值所以不需要使用参考：

How about passing the event handler directly to <Input>? This way you pass the on change event directly to your parent (grandparent of <Input>) and you can extract the value from event.target.value so no need to use refs:

注意：您可能需要 bind 您的父构造函数中的 onUserInputChange（）的上下文，因为事件处理程序默认情况下发生事件作为上下文的元素：

Note: You might have to bind the context of onUserInputChange() in you parent's constructor because event handlers have the element on which the event happened as their context by default:

父

class AddConditionDashboard extends React.Component {

  constructor(props) {
    // ...

    // bind the context for the user input event handler
    // so we can use `this` to reference `AddConditionDashboard`
    this.onUserInputChange = this.onUserInputChange.bind(this);
  }

  onUserInputChange({ target }) {
    const { value: conditionTitle } = target;
    this.setState({
     conditionTitle
    });
  }

  render() {
    // ...

    <AddConditionSelect segmentId={segmentId} 
                        conditionTitle={this.state.conditionTitle} 
                        onUserInputChange={this.onUserInputChange} // <-- pass event handler to child that will pass it on to <Input>
    />

    // ...
  }
  // ...

孩子：

class AddConditionSelect extends React.Component {

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

    return (
      <div>
        // ...

        <Input value={this.props.conditionTitle} 
               label="" 
               type="text" 
               buttonLabel="Add Condition" 
               name="add_segment" 
               onChange={this.props.onUserInputChange} // <-- Use the grandparent event handler
               placeholder="Condition Title"
        />

       // ...
     </div>
    );
  }
}

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