Dictionaries in Swift
From the Swift cheat sheet · Collections · verified Jul 2026
Dictionaries
Key-value pair collections
swift
// Dictionary creation
var scores: [String: Int] = ["Alice": 95, "Bob": 87]
var emptyDict: [String: String] = [:]
// Dictionary operations
scores["Charlie"] = 92 // Add/update
scores.removeValue(forKey: "Bob")
let aliceScore = scores["Alice"] // Optional Int?
// Dictionary methods
for (name, score) in scores {
print("\(name): \(score)")
}
let names = Array(scores.keys)
let values = Array(scores.values)
// Default values
let defaultScore = scores["Unknown", default: 0]💡 Dictionary access returns optionals since keys might not exist
⚡ Use default parameter to avoid nil checking
📌 merge() is powerful for combining dictionaries with custom logic
🟢 Dictionary(grouping:by:) creates dictionaries from sequences