Button

export const ButtonBlock = ({buttonType, value, handleSubmit}) => (
  <div className="btn-block" onClick={handleSubmit}>
    <a className={`btn ${buttonType}`} href="javascript:void(0);">
      {value}
    </a>
  </div>
)

InputGroup

const InputGroup = props => {
//请注意下面的 ...others
  const { iconLeft, iconRight, updateValue, ...others } = props
  return (
    <section className="input-group-dark">
      <i className={`icon icon-left ${iconLeft}`} />
      <input
        className="input input-block"
        onChange={event => updateValue(event.target.value.trim())}
        /*...others 不明白的话翻一下 ES6 工具书*/ 
        {...others}
      />
      {iconRight ? <i className={`icon icon-right ${iconRight}`} /> : ''}
    </section>
  )
}

引入不同

import { ButtonBlock } from '...Button';
import InputGroup from '....InputGroup';

因为 Button 组件可能会弄好几个 button ，不确定

栗子🌰

class LoginForm extends React.Component {
  constructor(props){
    super(props);
    this.state = {
      userName : '',
    }
    this._handleLogin = this._handleLogin.bind(this)
  }

   _handleLogin() {
     let userName = this.state.userName;
     //点击提交按钮可以拿到输入框里的值
  }
  render() {
    return (
      <InputGroup
            iconLeft="phone"
            updateValue={ userName => this.setState({userName}) }
            type="tel"
            pattern="[0-9]*"
            placeholder="请输入手机号"
            // type，pattern，placeholder 这些属性可以随意添加，因为 InputGroup里有{...other}
        />
      <ButtonBlock
            buttonType="btn-dark"
            value="立即登录"
            handleSubmit={this._handleLogin}
        />
  )

可以不用 this.state 吗？

可以！
updateValue={ userName => this.setState({userName}) }
反正输入框的值 userName 已经拿到，我猜可以这么写（未测试）：

  submit(value) {
    console.log(value)
  }
  render() {
    let value;
    return (
      <form submit={() =>this.submit(value)}>
        <InputGroup
            iconLeft="phone"
            updateValue={ userName => value  = userName  }
            type="tel"
            pattern="[0-9]*"
            placeholder="请输入手机号"
          />
      </form>
  )