Chuỗi ký tự (String) trong Swift

let name = "Swift"
let greeting: String = "Hello"
 
// Multi-line
let multiLine = """
    Line 1
    Line 2
    """
 
// Empty string
let empty = ""
let isEmpty = empty.isEmpty  // true

let str = "  Swift Programming  "
 
// Case
print(str.uppercased())      // "  SWIFT PROGRAMMING  "
print(str.lowercased())      // "  swift programming  "
 
// Trim
let trimmed = str.trimmingCharacters(in: .whitespaces)
 
// Contains
print(str.contains("Swift"))  // true
 
// Replace
let replaced = str.replacingOccurrences(of: "Swift", with: "iOS")

let str = "Swift"
 
print(str.first)             // Optional("S")
print(str.last)              // Optional("t")
print(str.count)             // 5
 
// Substring
let index = str.index(str.startIndex, offsetBy: 2)
let sub = str[index...]      // "ift"

let csv = "a,b,c"
let parts = csv.split(separator: ",")  // ["a", "b", "c"]