我正在尝试在我的注册表单上使用 ReactJS 创建客户端验证。我使用http://validatejs.org/库进行验证，并使用https://github.com/jhudson8/react-semantic-ui组件来渲染语义 ui React 组件。这是代码。

var constraints = {
  email: {
    presence: true, 
    email:true
  }, 
  password: {
    presence: true,
    length: { minimum: 5 }
  }
}

var RegistrationForm = React.createClass({

  getInitialState: function() {
    return { 
      data: {},
      errors: {}
    };
  },

  changeState: function () {
    this.setState({
      data: {
        email: this.refs.email.getDOMNode().value,
        password: this.refs.password.getDOMNode().value,
        password_confirmation:  this.refs.password_confirmation.getDOMNode().value
      }
    });
    console.log("State after update");
    console.log(this.state.data);
  },

  handleChange: function(e) {
    this.changeState();
    var validation_errors = validate(this.state.data, constraints);

    if(validation_errors){
      console.log(validation_errors);
      this.setState({errors: validation_errors});
    }
    else
      this.setState({errors: {}});
  },

  handleSubmit: function(e) {
    e.preventDefault();
    //code left out..
  },

  render: function() {
    var Control = rsui.form.Control;
    var Form = rsui.form.Form;
    var Text = rsui.input.Text;
    var Button = rsui.form.Button;
    return (
      <Form onSubmit={this.handleSubmit} onChange={this.handleChange}>
        <h4 className="ui dividing header">New User Registration</h4>
        <Control label="Email" error={this.state.errors.email}>
          <Text name="email" type="email" ref="email"  key="email" value={this.state.data.email}></Text>
        </Control>
        <Control label="Password" error={this.state.errors.password}>
          <Text name="password" type="password" ref="password" key="password" value={this.state.data.password}></Text>
        </Control>
        <Control label="Password Confirmation">
          <Text name="password_confirmation" type="password" ref="password_confirmation" key="password_confirmation" value={this.state.data.password_confirmation}></Text>
        </Control>
        <Button> Register </Button>
      </Form>);
  }
});

我遇到的问题是，当我调用 this.setState 时，状态不会立即更新，因此当我调用 validate(this.state.data,constraints) 时，我正在验证以前的状态，因此用户的 UI 体验变得很奇怪，例如：

如果我的电子邮件字段中有“example@em”并输入“a”，它将验证字符串“example@em”而不是“example@ema”，因此本质上它总是在新的击键之前验证状态。我一定在这里做错了什么。我知道组件的状态不会立即更新，只有在渲染完成后。

我应该在渲染函数中进行验证吗？

- - 解决方案 - -

像 Felix Kling 建议的那样向 setState 添加回调解决了它。这是带有解决方案的更新代码：

var RegistrationForm = React.createClass({

  getInitialState: function() {
    return { 
      data: {},
      errors: {}
    };
  },

  changeState: function () {
    this.setState({
      data: {
        email: this.refs.email.getDOMNode().value,
        password: this.refs.password.getDOMNode().value,
        password_confirmation: this.refs.password_confirmation.getDOMNode().value
      }
    },this.validate);
  },

  validate: function () {
    console.log(this.state.data);
    var validation_errors = validate(this.state.data, constraints);

    if(validation_errors){
      console.log(validation_errors);
      this.setState({errors: validation_errors});
    }
    else
      this.setState({errors: {}});
  },

  handleChange: function(e) {
    console.log('handle change fired');
    this.changeState();
  },

  handleSubmit: function(e) {
    e.preventDefault();
    console.log(this.state);
  },

  render: function() {
    var Control = rsui.form.Control;
    var Form = rsui.form.Form;
    var Text = rsui.input.Text;
    var Button = rsui.form.Button;
    return (
      <Form onSubmit={this.handleSubmit} onChange={this.handleChange}>
        <h4 className="ui dividing header">New Rowing Club Registration</h4>
        <Control label="Email" error={this.state.errors.email}>
          <Text name="email" type="email" ref="email"  key="email" value={this.state.data.email}></Text>
        </Control>
        <Control label="Password" error={this.state.errors.password}>
          <Text name="password" type="password" ref="password" key="password" value={this.state.data.password}></Text>
        </Control>
        <Control label="Password Confirmation">
          <Text name="password_confirmation" type="password" ref="password_confirmation" key="password_confirmation" value={this.state.data.password_confirmation}></Text>
        </Control>
        <Button> Register </Button>
      </Form>);
  }
});

--- 更好的解决方案 -----

请参阅下面的 FakeRainBrigand 的解决方案。