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 )
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 creates a file, adds data to the file, displays the file,
// appends more data to the file, displays the file, and then deletes the file.
// It will not run if the file already exists.
//
// References:
// https://www.mathsisfun.com/temperature-conversion.html
// https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html
import Foundation
func fileExists(filename:String) -> Bool {
let fileManager = FileManager.default
return fileManager.fileExists(atPath:filename)
}
func calculateFahrenheit(celsius:Double) -> Double {
var fahrenheit: Double
fahrenheit = celsius * 9 / 5 + 32
return fahrenheit
}
func createFile(filename:String) {
var text: String
var fahrenheit: Double
text = "Celsius,Fahrenheit\n"
for celsius in stride(from: 0.0, through: 50.0, by: 1.0) {
fahrenheit = calculateFahrenheit(celsius:celsius)
text += String(celsius) + "," + String(fahrenheit) + "\n"
}
do {
try text.write(toFile: filename, atomically: true, encoding: .utf8)
} catch {
print("Error creating ", filename)
print(error.localizedDescription)
}
}
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 appendFile(filename:String) {
var text: String
var fahrenheit: Double
do {
text = try String(contentsOfFile: filename, encoding: .utf8)
for celsius in stride(from: 51.0, through: 100.0, by: 1.0) {
fahrenheit = calculateFahrenheit(celsius:celsius)
text += String(celsius) + "," + String(fahrenheit) + "\n"
}
try text.write(toFile: filename, atomically: true, encoding: .utf8)
} catch {
print("Error appending to ", filename)
print(error.localizedDescription)
}
}
func deleteFile(filename:String) {
do {
let fileManager = FileManager.default
try fileManager.removeItem(atPath:filename)
} catch {
print("Error deleting", filename)
print(error.localizedDescription)
}
}
func main() {
let filename:String = "~file.txt"
if (fileExists(filename:filename)) {
print("File already exists.")
}
else {
createFile(filename:filename)
readFile(filename:filename)
appendFile(filename:filename)
readFile(filename:filename)
deleteFile(filename:filename)
}
}
main()
Output
Celsius,Fahrenheit
0.0,32.0
1.0,33.8
2.0,35.6
3.0,37.4
...
98.0,208.4
99.0,210.2
100.0,212.0