Dictionary trong Swift

// Dictionary literal
var scores = ["Alice": 95, "Bob": 87, "Charlie": 92]
 
// Empty dictionary
var emptyDict: [String: Int] = [:]
var anotherDict = [String: String]()
 
// Type inference
var ages = ["Alice": 25, "Bob": 30]  // [String: Int]

let scores = ["Alice": 95, "Bob": 87]
 
// Subscript - trả về Optional
let aliceScore = scores["Alice"]  // Optional(95)
 
if let score = scores["Alice"] {
    print("Alice: \(score)")
}
 
// Default value
let bobScore = scores["Bob"] ?? 0

var scores = ["Alice": 95]
 
// Thêm mới
scores["Bob"] = 87
 
// Sửa
scores["Alice"] = 98
 
// updateValue - trả về old value
if let oldScore = scores.updateValue(90, forKey: "Alice") {
    print("Old score: \(oldScore)")
}

var scores = ["Alice": 95, "Bob": 87]
 
// Gán nil
scores["Alice"] = nil
 
// removeValue
if let removed = scores.removeValue(forKey: "Bob") {
    print("Removed: \(removed)")
}
 
// Xóa tất cả
scores.removeAll()

let scores = ["Alice": 95, "Bob": 87, "Charlie": 92]
 
// Keys và values
for (name, score) in scores {
    print("\(name): \(score)")
}
 
// Chỉ keys
for name in scores.keys {
    print(name)
}
 
// Chỉ values
for score in scores.values {
    print(score)
}

let scores = ["Alice": 95, "Bob": 87]
 
print(scores.count)          // 2
print(scores.isEmpty)        // false
print(scores.keys)           // ["Alice", "Bob"]
print(scores.values)         // [95, 87]
 
// Convert keys/values to Array
let names = Array(scores.keys)
let scoresList = Array(scores.values)