如何以编程方式更新Redux表单中的字段值？

const initialState = {
  username: '',
  password: '',
  email: ''
};

const updateFormField = (fieldName, value) => {
  return {
    type: 'UPDATE_FORM_FIELD',
    fieldName,
    value
  };
};

const formReducer = (state = initialState, action) => {
  switch (action.type) {
    case 'UPDATE_FORM_FIELD':
      return {
        ...state,
        [action.fieldName]: action.value
      };
    default:
      return state;
  }
};

import { connect } from 'react-redux';
import { updateFormField } from './actions';

class MyForm extends React.Component {
  handleInputChange = (event) => {
    const { name, value } = event.target;
    this.props.updateFormField(name, value);
  };

  render() {
    return (
      <form>
        <input
          type="text"
          name="username"
          value={this.props.username}
          onChange={this.handleInputChange}
        />
        <input
          type="password"
          name="password"
          value={this.props.password}
          onChange={this.handleInputChange}
        />
        <input
          type="email"
          name="email"
          value={this.props.email}
          onChange={this.handleInputChange}
        />
      </form>
    );
  }
}

const mapStateToProps = (state) => {
  return {
    username: state.username,
    password: state.password,
    email: state.email
  };
};

const mapDispatchToProps = {
  updateFormField
};

export default connect(mapStateToProps, mapDispatchToProps)(MyForm);