title: _react2.default.PropTypes.function is undefined
body: <p>So I have a Button component</p>
  
  <pre><code>import React, { Component } from 'react';
  import { View, Text, TouchableNativeFeedback } from 'react-native';
  
  class Button extends Component {
      generateComponent() {
          const { buttonStyle, textStyle } = this.styles;
          const { text } = this.props;
  
          switch (this.props.platform) {
              case 'android':
                  return (
                      &lt;TouchableNativeFeedback onPress={this.props.onPress}&gt;
                          &lt;View style={buttonStyle}&gt;
                              &lt;Text style={textStyle}&gt;{text}&lt;/Text&gt;
                          &lt;/View&gt;
                      &lt;/TouchableNativeFeedback&gt;
                  );
              case 'ios':
                  return 0;
          }
      }
  
      render() {
          return (
              &lt;View&gt;
                  { this.generateComponent() }
              &lt;/View&gt;
          );
      }
  
      styles = {
          buttonStyle: {
              borderRadius: 100,
              justifyContent: 'center',
              height: parseInt(this.props.size, 10),
              width: parseInt(this.props.size, 10),
              backgroundColor: this.props.color,
              elevation: 3
          },
          textStyle: {
              fontWeight: 'bold',
              fontSize: parseInt(this.props.fontSize, 10),
              lineHeight: parseInt(this.props.fontSize, 10)
                  + Math.floor(parseInt(this.props.fontSize, 10) / 10) + 1,
              color: this.props.fontColor,
              textAlign: 'center'
          }
      }
  }
  
  Button.propTypes = {
      text: React.PropTypes.string.isRequired,
      platform: React.PropTypes.string.isRequired,
      size: React.PropTypes.string.isRequired,
      color: React.PropTypes.string.isRequired,
      fontColor: React.PropTypes.string.isRequired,
      fontSize: React.PropTypes.string.isRequired,
      onPress: React.PropTypes.function.isRequired
  };
  
  export default Button;
  </code></pre>
  
  <p>And I call this component in the component Home</p>
  
  <pre><code>import React, { Component } from 'react';
  import { View } from 'react-native';
  import Metas from '../components/Metas';
  import Button from '../components/Button';
  
  export default class Home extends Component {
      constructor(props) {
          super(props);
          this.state = { metas: ['Meta 1', 'Meta 2', 'Meta 3'] };
      }
  
      render() {
          return (
              &lt;View&gt;
                  &lt;Metas data={ this.state.metas } /&gt;
                  &lt;Button
                      text="+"
                      platform={ this.props.platform }
                      onPress={ this._handleButtonPress }
                      size='50'
                      fontSize='25'
                      color='#FFD600'
                      fontColor='white'
                  /&gt;
              &lt;/View&gt;
          );
      }
  
      _handleButtonPress() {
          console.log("Hello!");
      }
  }
  
  Home.propTypes = {
      platform: React.PropTypes.string.isRequired
  };
  </code></pre>
  
  <p>The problem is that if I include the PropTypes I get an error saying that the onPress prop is undefined.</p>
  
  <p>I do not understand why I recieve this error. I consoled logged the typeof onPress and it prints function.</p>
  
  <p>Any suggestion??</p>