Arrays, Dictionaries, and Sets

Arrays, Dictionaries, and Sets

Swift gives you three main collection types to store groups of data. Arrays are ordered lists—you can create them with type annotations like [String] or Array<String>.

var fruits = ["Apple", "Banana", "Orange"]
fruits.append("Mango")
fruits.remove(at: 1)
print(fruits.contains("Apple")) // true

Dictionaries store key-value pairs. Think of them like a real dictionary—look up a word (key) to find its definition (value). Accessing a dictionary returns an optional because the key might not exist:

var scores = ["Alice": 95, "Bob": 87, "Charlie": 92]
if let aliceScore = scores["Alice"] {
    print("Alice scored \(aliceScore)")
}

Sets are unordered collections of unique values. They're perfect when you need to ensure no duplicates. Create them with Set<Type> syntax:

var uniqueNumbers: Set<Int> = [1, 2, 3, 2, 1]
print(uniqueNumbers) // [1, 2, 3]

Arrays come with powerful methods like filter and map for transforming data. These functional programming tools make your code more expressive and concise.