Sets in Dart

A Set is a collection of unique elements - think of it like a bag where you can't have duplicates! If you try to add the same item twice, the set will just ignore the duplicate. Sets are perfect when you need to store a collection of items where uniqueness matters.

Creating Sets

You can create sets in several ways:

// Empty set
var emptySet = <String>{};
Set<int> numbers = {};

// Set with initial values
var fruits = {'apple', 'banana', 'orange'};
Set<String> colors = {'red', 'green', 'blue'};

// Using Set constructor
var animals = Set<String>();
animals.addAll(['cat', 'dog', 'bird']);

Key Properties of Sets

Property	Description	Example
length	Number of elements in the set	fruits.length
isEmpty	Returns true if set is empty	emptySet.isEmpty
isNotEmpty	Returns true if set has elements	fruits.isNotEmpty

Adding Elements

var hobbies = <String>{};

// Add single element
hobbies.add('reading');
hobbies.add('swimming');
hobbies.add('reading'); // This won't be added (duplicate!)

print(hobbies); // {reading, swimming}

// Add multiple elements
hobbies.addAll(['cooking', 'dancing', 'reading']);
print(hobbies); // {reading, swimming, cooking, dancing}

Removing Elements

var numbers = {1, 2, 3, 4, 5};

// Remove specific element
numbers.remove(3);
print(numbers); // {1, 2, 4, 5}

// Remove elements that match a condition
numbers.removeWhere((num) => num > 3);
print(numbers); // {1, 2}

// Clear all elements
numbers.clear();
print(numbers); // {}

Checking for Elements

var languages = {'Dart', 'JavaScript', 'Python'};

// Check if element exists
print(languages.contains('Dart')); // true
print(languages.contains('Java')); // false

// Check if any element matches condition
print(languages.any((lang) => lang.startsWith('P'))); // true

// Check if all elements match condition
print(languages.every((lang) => lang.length > 3)); // true

Set Operations

Sets support mathematical operations like union, intersection, and difference:

var setA = {1, 2, 3, 4};
var setB = {3, 4, 5, 6};

// Union (combine both sets)
var union = setA.union(setB);
print(union); // {1, 2, 3, 4, 5, 6}

// Intersection (common elements)
var intersection = setA.intersection(setB);
print(intersection); // {3, 4}

// Difference (elements in setA but not in setB)
var difference = setA.difference(setB);
print(difference); // {1, 2}

Iterating Through Sets

var cities = {'New York', 'London', 'Tokyo', 'Paris'};

// Using for-in loop
for (var city in cities) {
  print('City: $city');
}

// Using forEach method
cities.forEach((city) => print('Visiting $city'));

// Converting to list for indexed access
var cityList = cities.toList();
print('First city: ${cityList[0]}');

When to Use Sets

Sets are ideal when you need to:

• Store unique values only
• Perform mathematical set operations
• Check membership quickly
• Remove duplicates from a collection

Remember: Sets don't maintain insertion order (except for LinkedHashSet), so if order matters, consider using a List instead!