What are common string processing methods in Swift? How to perform string concatenation, substring, replacement, and search?

What are common string processing methods in Swift? How to perform string concatenation, substring, replacement, and search?

Swift provides rich string processing methods, including concatenation, substring, replacement, search, and other operations. Swift's String type is a value type that supports Unicode characters.

String Concatenation:

swift
// Using + operator
let str1 = "Hello"
let str2 = "World"
let combined = str1 + ", " + str2  // "Hello, World"

// Using += operator
var greeting = "Hello"
greeting += ", World"  // "Hello, World"

// Using string interpolation
let name = "John"
let age = 30
let message = "My name is \(name) and I'm \(age) years old"

// Using append method
var text = "Hello"
text.append(", World")  // "Hello, World"

String Substring:

swift
let str = "Hello, World"

// Using prefix and suffix
let prefix = str.prefix(5)      // "Hello"
let suffix = str.suffix(6)      // "World"

// Using dropFirst and dropLast
let withoutFirst = str.dropFirst()     // "ello, World"
let withoutLast = str.dropLast()       // "Hello, Worl"

// Using indices
let startIndex = str.startIndex
let endIndex = str.index(str.startIndex, offsetBy: 5)
let substring = str[startIndex..<endIndex]  // "Hello"

// Using range
let range = str.range(of: "World")!
let substring2 = str[range]  // "World"

String Replacement:

swift
let str = "Hello, World"

// Replace single character
let replaced = str.replacingOccurrences(of: "World", with: "Swift")
// "Hello, Swift"

// Using closure for replacement
let replaced2 = str.replacingOccurrences(of: "o", with: "O")
// "HellO, WOrld"

// Using closure for complex replacement
let replaced3 = str.replacingOccurrences(of: "[aeiou]", with: "", options: .regularExpression)
// "Hll, Wrld"

String Search:

swift
let str = "Hello, World"

// Check if contains
let containsHello = str.contains("Hello")  // true
let containsSwift = str.contains("Swift")  // false

// Find substring
if let range = str.range(of: "World") {
    print("Found at range: \(range)")
}

// Find prefix and suffix
let hasPrefix = str.hasPrefix("Hello")  // true
let hasSuffix = str.hasSuffix("World")  // true

// Find character
let firstIndex = str.firstIndex(of: ",")  // Optional(String.Index)

String Splitting:

swift
let str = "apple,banana,orange"

// Split by character
let components = str.components(separatedBy: ",")
// ["apple", "banana", "orange"]

// Split by character set
let whitespace = "Hello    World"
let words = whitespace.components(separatedBy: .whitespaces)
// ["Hello", "World"]

String Case Conversion:

swift
let str = "Hello, World"

let uppercased = str.uppercased()  // "HELLO, WORLD"
let lowercased = str.lowercased()  // "hello, world"
let capitalized = str.capitalized  // "Hello, World"

String Trimming:

swift
let str = "   Hello, World   "

let trimmed = str.trimmingCharacters(in: .whitespaces)
// "Hello, World"

let trimmed2 = str.trimmingCharacters(in: .whitespacesAndNewlines)
// "Hello, World"

String Length and Characters:

swift
let str = "Hello, World"

let count = str.count  // 13
let isEmpty = str.isEmpty  // false

let firstChar = str.first  // Optional("H")
let lastChar = str.last  // Optional("d")

let chars = Array(str)  // ["H", "e", "l", "l", "o", ",", " ", "W", "o", "r", "l", "d"]

Best Practices:

1. Use string interpolation to improve readability
2. Pay attention to string index usage
3. Use contains, hasPrefix, hasSuffix for quick checks
4. Use replacingOccurrences for string replacement
5. Be aware of Unicode character handling