Swift Examples

Strings

// This program demonstrates string functions.

import Foundation

func main() {
    let string:String = "Hello"

    print("string: " + string)
    print("string.lowercased(): " + string.lowercased())
    print("string.uppercased(): " + string.uppercased())
    print("find(string, \"e\"): " + String(find(string:string, character:"e")))
    print("string.count: " + String(string.count))
    print("string.replacingOccurrences(of:\"H\", with:\"j\"): " + string.replacingOccurrences(of:"H", with:"j"))
    print("string.reversed(): " + String(string.reversed()))
    print("substring(2, 2): " + substring(string:string, start:2, length:2))
    print("string.trimmingCharacters(\"H\"): " + string.trimmingCharacters(in:CharacterSet.init(charactersIn: "H")))

    let name:String = "Bob"
    let value:Double = 123.456
    print("\(name) earned $" + String(format:"%.2f", value))
}

func find(string:String, character:Character) -> Int {
    var result: Int

    if let index = string.firstIndex(of:character) {
        result = string.distance(from: string.startIndex, to: index)
    } else {
        result = -1
    }
    return result
}

func substring(string:String, start:Int, length:Int) -> String {
    let startIndex = string.index(string.startIndex, offsetBy: start)
    let endIndex = string.index(string.startIndex, offsetBy: start + length - 1)
    return String(string[startIndex...endIndex])
}

main()

Output

string: Hello
string.lowercased(): hello
string.uppercased(): HELLO
find(string, "e"): 1
string.count: 5
string.replacingOccurrences(of:"H", with:"j"): jello
string.reversed(): olleH
substring(2, 2): ll
string.trimmingCharacters("H"): ello
Bob earned $123.46

Files

// This program demonstrates reading a text file with exception handling.

// References:
//  https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html

import Foundation

func readFile(filename:String) {
    var text = ""

    do {
        text = try String(contentsOfFile: filename, encoding: .utf8)

        let lines = text.components(separatedBy:"\n")
        for line in lines {
            print(line)
        }
    } catch {
        print("Error reading " + filename)
        print(error.localizedDescription)
    }
}

func main() {
    let filename:String = "temperature.txt"

    readFile(filename:filename)
}
        
main()

Output

Celsius,Fahrenheit
0,32
10,50
20,68
...
80,176
90,194
100,212

References

• Wikiversity: Computer Programming