Exercise: Restaurant ratings (a weird outcome)

main.dart

void main() {
  var restaurants = [
    {
      'name': 'Pizza Mario',
      'cuisine': 'Italian',
      'ratings': [5.0, 3.5, 4.5],
    },
    {
      'name': 'Chez Anne',
      'cuisine': 'French',
      'ratings': [5.0, 4.5, 4.0],
    },
    {
      'name': 'Navaratna',
      'cuisine': 'Indian',
      'ratings': [4.0, 4.5, 4.0],
    },
  ];

  for (var restaurant in restaurants) {
    final ratings = restaurant['ratings'] as List<double>;
    
    // I expected this to update a *copy* of the restaurant Map thinking that 'restaurant' is passed by value. But...
    restaurant['avgRating'] = ratings.reduce((a, b) => a + b) / ratings.length;
  }

  // I printed the original collection here (on accident) and it showed the restaurants with the additional key.
  print(restaurants);

  /* 
   * Formatted output.
   * [
   *   {name: Pizza Mario, cuisine: Italian, ratings: [5.0, 3.5, 4.5], avgRating: 4.333333333333333},
   *   {name: Chez Anne, cuisine: French, ratings: [5.0, 4.5, 4.0], avgRating: 4.5},
   *   {name: Navaratna, cuisine: Indian, ratings: [4.0, 4.5, 4.0], avgRating: 4.166666666666667}
   * ]
   */
}