Lists and Maps in Dart

What are Iterable?

• Its a collection of objects that can be iterated over, meaning you can access each element one by one.
• In Dart, the two main types of iterables are Lists and Maps.

Lists in Dart

• Its the one of the useful object in Dart and also called as Array in other programming languages.
• It is an ordered collection of items where each item can be accessed using its index.

How to Declare a List in Dart?

• You can declare a List using the List keyword followed by the data type of the elements inside angle brackets <> and then use square brackets [] to initialize the list with values.

void main() {
  // Declaring a List of integers
  List<int> numbers = [1, 2, 3, 4, 5];

  // Printing the List
  print('Numbers: $numbers');
}

Accessing List Elements

• You can access elements in a List using their index, which starts from 0 for the first element.

void main() {
  List<String> fruits = ['Apple', 'Banana', 'Orange'];

  // Accessing elements using index
  print('First fruit: ${fruits[0]}'); // Apple
  print('Second fruit: ${fruits[1]}'); // Banana
}

Common List Operations

• Adding Elements: You can add elements to a List using the add() method.
• Removing Elements: You can remove elements using the remove() method.
• Iterating through a List: You can use a for loop or forEach() or map() method to iterate through the elements of a List.

void main() {
  List<String> colors = ['Red', 'Green', 'Blue'];

  // Adding an element
  colors.add('Yellow');
  print('Colors after adding Yellow: $colors');

  // Removing an element
  colors.remove('Green');
  print('Colors after removing Green: $colors');

  // Iterating through the List Using for loop
  print('Iterating through colors:');
  for (var color in colors) {
    print(color);
  }
  // Iterating using forEach method
  print('Iterating using forEach method:');
  colors.forEach((color) {
    print(color);
  });
  // Iterating using map method
  print('Iterating using map method:');
  colors.map((color) => print(color)).toList();

}

Maps in Dart

• A Map is a collection of key-value pairs, where each key is unique and is used to access its corresponding value.
• It is also known as Dictionary or HashMap in other programming languages.

How to Declare a Map in Dart?

• You can declare a Map using the Map keyword followed by the data types of the keys and values inside angle brackets <> and then use curly braces {} to initialize the map with key-value pairs.

void main() {
  // Declaring a Map with String keys and int values
  Map<String, int> ages = {
    'Alice': 25,
    'Bob': 30,
    'Charlie': 35,
  };

  // Printing the Map
  print('Ages: $ages');
}

Accessing Map Elements

• You can access values in a Map using their corresponding keys.

void main() {
  Map<String, String> capitals = {
    'USA': 'Washington, D.C.',
    'India': 'New Delhi',
    'France': 'Paris',
  };

  // Accessing values using keys
  print('Capital of USA: ${capitals['USA']}'); // Washington, D.C.
  print('Capital of India: ${capitals['India']}'); // New Delhi
}

Common Map Operations

• Adding Key-Value Pairs: You can add key-value pairs to a Map using the assignment operator =.
• Removing Key-Value Pairs: You can remove key-value pairs using the remove() method.
• Iterating through a Map: You can use a for loop or forEach() method to iterate through the key-value pairs of a Map.

void main() {
  Map<String, double> prices = {
    'Apple': 1.5,
    'Banana': 0.75,
    'Orange': 1.25,
  };

  // Adding a key-value pair
  prices['Grapes'] = 2.0;
  print('Prices after adding Grapes: $prices');

  // Removing a key-value pair
  prices.remove('Banana');
  print('Prices after removing Banana: $prices');

  // Iterating through the Map Using for loop
  print('Iterating through prices:');
  for (var entry in prices.entries) {
    print('${entry.key}: \$${entry.value}');
  }
  // Iterating using forEach method
  print('Iterating using forEach method:');
  prices.forEach((key, value) {
    print('$key: \$${value}');
  });
}

Rescources to Learn Dart

• Courses and Tutorials: Dart And Flutter Series on Youtube ("https://youtube.com/playlist?list=PL9eMLfd38heN2BbPEng6W9qBLl3oJAtwD&si=w_gsoYnIUSzFBLeR")
• Official Dart Documentation: The official Dart website (https://dart.dev) provides comprehensive documentation, tutorials, and guides to help you get started with Dart programming.
• DartPad: An online Dart editor (https://dartpad.dev) that allows you to write, run, and share Dart code directly in your web browser without any setup.
• Flutter Documentation: Since Dart is primarily used with Flutter, the official Flutter documentation (https://flutter.dev/docs) is an excellent resource for learning how to build apps using Dart and Flutter together.

What's Next?

• In the Next Lesson, we will explore Classes in Dart. See you there! (Next: Classes in Dart )