App.js

import { StatusBar } from 'expo-status-bar';
import React, { useState } from 'react';
import { Button, FlatList, StyleSheet, View } from 'react-native';
import GoalInput from './components/GoalInput';
import GoalItem from './components/GoalItem';

export default function App() {
  const [courseGoals, setCourseGoals] = useState([]);
  const [isAddMode, setIsAddMode] = useState(false);

  const addGoalHandler = goal => {
    setCourseGoals(currentGoals => [
      ...currentGoals,
      { id: Math.random().toString(), value: goal },
    ]);
    setIsAddMode(false);
  };

  const removeGoalHandler = goalId => {
    setCourseGoals(currentGoals => {
      return currentGoals.filter(goal => goal.id !== goalId);
    });
  };

  const cancelGoalAdditionHandler = () => setIsAddMode(false);

  return (
    <View style={styles.screen}>
      <Button title='Add new goal' onPress={() => setIsAddMode(true)} />
      <GoalInput
        visible={isAddMode}
        onAddGoal={addGoalHandler}
        onCancel={cancelGoalAdditionHandler}
      />
      <FlatList
        keyExtractor={(item, index) => item.id}
        data={courseGoals}
        renderItem={itemData => (
          <GoalItem onDelete={removeGoalHandler} goal={itemData.item} />
        )}
      />
      <StatusBar style='auto' />
    </View>
  );
}

const styles = StyleSheet.create({
  screen: {
    padding: 50,
  },
});