App.js

// In App.js in a new project

import * as React from 'react';
import { View, Text, Button, TextInput, StyleSheet } from 'react-native';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import Login from './src/pages/Login';
import Signup from './src/pages/Signup';
//import styles from "./assets/styles.js";
import UserFeed from './src/pages/UserFeed';

const Stack = createStackNavigator();
// const dummyMatches = [
//   {
//     name: "Nick",
//     id: 1,
//     body: "Javascript extraordinaire",
//     toLearn: "Python",
//     toTeach: "Javascript",
//   },
//   {
//     name: "Hideaki",
//     id: 2,
//     body: "Cool music cat",
//     toLearn: "Javascript",
//     toTeach: "C++",
//   },
//   {
//     name: "Matt",
//     id: 3,
//     body: "Hacking is my life",
//     toLearn: "C++",
//     toTeach: "Python",
//   },
// ];

const defUserObj = {
  isLoggedIn : false,
  userInfo : {
    id : '',
    username: '',
    email: '',
    toTeach: '', 
    toLearn: '' 
  }
};
const headerStyle = {
  headerStyle: { backgroundColor: '#036bfc' },
  headerTintColor: '#fff',
  headerTitleStyle: {
    fontWeight: '700',
  },
};

function App() {
  const [matches, setMatches] = React.useState([]); 
  const [fetching, setFetching] = React.useState(false);
  const [userInfo, setUserInfo] = React.useState(defUserObj);

  const getMatches = (id, toTeach, toLearn) => {
    const body = {
      "learn_tech_id": 2,
      "teach_tech_id_array": [4,5]
    };
    const options = {
      method: 'POST',
      headers: {
        'Content-Type' : 'application/json'
      },
      body: JSON.stringify(body)
    }
    fetch('http://192.168.1.6:3000/user/matches', options)
    .then(res => res.json())
    .then(data => {
      console.log('just got back: ', data)
      setMatches(data)
    })
    .catch(err => console.log(err))
  }; 
  
  return (
    <NavigationContainer>
      <Stack.Navigator initialRouteName="Log in">
        <Stack.Screen name="Signup" component={Signup} options={headerStyle} />
        <Stack.Screen name="Log in" options={headerStyle}>
        {props => (<Login {...props} logIn={getMatches} />)}
        </Stack.Screen>
        <Stack.Screen
          name="User Feed"
          options={headerStyle}
        >
          {props => (<UserFeed {...props} matches={matches} />)}
        </Stack.Screen>
      </Stack.Navigator>
    </NavigationContainer>
  );
  
}

export default App;