If/else statements in React Native

I have a problem with if/else statements in React Native.

For example, I have two states:

  onOpen() {
    this.setState({
      index: 1
    });
  }

  onClose() {
    this.setState({
      index: 0
    });
  }

I need to set State index: 0, when toggle close and index: 1, when toggle open.

<TouchableOpacity onPress={() => 
{index === 0 ? navigator.toggleDrawer(this.onClose()) 
: navigator.toggleDrawer(this.onOpen())}}>

For now, when I click on menu-button I receive index 0 every time, but they should change on 1 and back. Thanks.

Component:

import React from 'react';
import {
  TouchableOpacity,
  Image 
} from 'react-native';

export default class Home extends Component {
  constructor(props) {
    super(props);
    this.state = {
      index: 0
    };
  }
  onOpen() {
    this.setState({
      index: 1
    });
  }

  onClose() {
    this.setState({
      index: 0
    });
  }

  render() {
    const { index } = this.state;
    return (
   <TouchableOpacity onPress={() => {index === 1 ? 
     navigator.toggleDrawer(this.onClose()) : 
     navigator.toggleDrawer(this.onOpen())}}>
        <Image
        source={require('something.png')}
       />    
   </TouchableOpacity>
    );
  }
}