// ..
async updateScheduledNotifications(callback? = undefined) {

  const scheduled = await firebase.notifications().getScheduledNotifications()
  const isCallbackAFunction = callback && typeOf(callback, 'function')
  this.setState({ scheduled }, ()=> isCallbackAFunction && callback.call(this, scheduled))

}

// componentWillMount is not recommended,
// it's heavy-handed on the old devices and will
// also be deprecated in the upcoming versions of react

componentDidMount() {
  this.updateScheduledNotifications()
}

render() {

  const emptyArray = []
  const { scheduled = emptyArray} = this.state

  if ( !scheduled.length ) return <View />
  return (
    scheduled.map((item, index)=> <Text key={index}>{ item.whatEverTitle }</Text>)
  )
}

// ..