Button.js

import React, { Component, PropTypes } from 'react'
import { TouchableOpacity, Text } from 'react-native'

// Your average run of the mill Button component.
export default class Button extends Component {
  render () {
    return (
      <TouchableOpacity onPress={this.props.onPress}>
        <Text>{this.props.text}</Text>
      </TouchableOpacity>
    )
  }
}

// configured from the parent
Button.propTypes = {
  onPress: PropTypes.func.isRequired,
  text: PropTypes.string.isRequired
}