title: AsyncStorage saying 'undefined is not an object'
body: <p>I am working on a shopping check list and want to save the checked items in local storage. However, setting up AsyncStorage hasnt been working for me saying undefined is not an object</p>
  
  <p>Here is my code: </p>
  
  <pre><code>import React from 'react';
  import { StyleSheet, Dimensions } from 'react-native';
  import { Container, Content, List, ListItem, Text, CheckBox, AsyncStorage } from 'native-base';
  
  export default class ShoppingListItem extends React.Component {
    constructor(props) {
      super(props);
      this.saveCheck = this.saveCheck.bind(this)
      this.state = {
        checked: false
      }
    }
  
    render() {
      return (
        &lt;ListItem style={styles.table}&gt;
          &lt;CheckBox 
            checked={this.state.checked}
            onPress={this.saveCheck}/&gt;
          &lt;Text&gt;{this.props.item[0]} {this.props.item[1]} {this.props.item[2]}&lt;/Text&gt;
        &lt;/ListItem&gt;
      );
    }
  
    // componentWillMount () {
    //   AsyncStorage.getItem(this.props.key).then((value) =&gt; {
    //      this.setState({checked: value});
    //   }).done();
    // }
  
    saveCheck () {
      console.log(this.state.checked)
      this.setState({checked: !this.state.checked})
      AsyncStorage.setItem('checked', JSON.stringify(this.state.checked))
    }
  }
  </code></pre>