A taste of Swift part3

//
//  main.swift
//  Taste_of_swift3
//
// exploring Apple's Swift language, part 3
// vegaseat   23jun2015    used Swift version 1.2

import Foundation

// class ...

// you can group functions that belong together in a class
// functions inside a class are called methods
class Animal {
    var name: String
    var sound: String
    // initializer is required
    init(name: String, sound: String) {
        self.name = name
        self.sound = sound
    }
    
    // a method of class Animal
    func speak() {
        println("\(self.name) goes '\(self.sound)'")
    }
    
    // this method returns a string argument
    func mood() -> String {
        return "\(self.name) looks happy today!"
    }
    
    // this method accepts an argument
    func hungry(yesno: String) {
        if yesno == "yes" {
            println("\(self.sound) \(self.sound) means \(self.name) is very hungry!")
        } else {
            println("Silence means not hungry!")
        }
    }
    
}

// create instance roger of class Dog
let roger = Animal(name: "Roger", sound: "woof")
// call some instance methods
roger.speak()           // Roger goes 'woof'
// this method returns an argument
println(roger.mood())   // Roger looks happy today!

// create an instance for a cat named Mitten
let mitten = Animal(name: "Mitten", sound: "meeow")
mitten.speak()           // Mitten goes 'meeow'
// this method takes an argument like "yes" or "no"
mitten.hungry("yes")     // meeow meeow means Mitten is very hungry!
mitten.hungry("no")      // Silence means not hungry!

println("---------------------")

class Person {
    var name: String
    var age: Int
    
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
    
    func intro() {
        println("Hello, I am \(self.name)!")
    }
    
    func detail() {
        if self.age < 0 {
            println("\(self.name)'s age is private!")
        } else {
            println("\(self.name) is \(self.age) years old.")
        }
    }
    
    func income() {
        println("My income is private information!")
    }
    
    func officeTalk() {
        // random office talk
        // generate a random integer beween 0 and 3
        var randInt = Int(arc4random_uniform(4))
        switch randInt {
        case 0: println("They don't pay enough!")
        case 1: println("Lousy coffee today!")
        case 2: println("It's cold here!")
        case 3: println("Look at that rear!")
        default: println("Bill's birthday today!")  // just in case
        }
    }
}

// create an immutable instance with let
let bob = Person(name: "Bob", age: 35)

bob.intro()  // Hello, I am Bob!
bob.detail() // Bob is 35 years old.

// you can change Bob's age, but not the instance
bob.age = 45

bob.detail()  // Bob is 45 years old.

// an age of less than zero makes age private info
let susan = Person(name: "Susan", age: -1)

susan.detail()      // Susan's age is private!
susan.income()      // My income is private information!
// office talk heard at random
susan.officeTalk()  // eg. "It's cold here!"

// class Pay inherits class Person
class Pay: Person {
    var pay: Float
    
    init(name: String, age: Int, pay: Float) {
        self.pay = pay
        // self.name and self.age shared with class Person
        super.init(name: name, age: age)
    }
    
    // age not required, will default to -1
    convenience init(name: String, pay: Float) {
        self.init(name: name, age: -1, pay: pay)
    }
    
    override func income() {
        println("\(name) gets $\(self.pay) a month pay")
    }
    
    // this method does not need init() data or class instance
    // call with Pay.bossTalk()
    class func bossTalk() {
        println("Management: Work hard and get more pay!")
    }
}

//let jim = Person(name: "Jim", age: 32)
let jimPay = Pay(name: "Jim", age: 32, pay: 4231.25)

// uses inherited intro()
jimPay.intro()   // Hello, I am Jim!
jimPay.detail()  // Jim is 32 years old.

// income() message is different, applied override
jimPay.income()  // Jim gets $4231.25 a month pay

// leave the age off, will use convenience init() with age default value
let tomPay = Pay(name: "Tom", pay: 3781.57)

tomPay.intro()       // Hello, I am Tom!
tomPay.detail()      // Tom's age is private!
tomPay.income()      // Tom gets $3781.57 a month pay
tomPay.officeTalk()  // eg. "They don't pay enough!"

// a method that doesn't use init() data
Pay.bossTalk()  // Management: Work hard and get more pay!

println("---------------------")

// writing/reading a text file using a class ...
class File {
    // "class func" allows use of File.read(path) method call
    // an initiallizer is not required
    // utf8 is default encoding
    class func read(path: String, utf8: NSStringEncoding =
        NSUTF8StringEncoding) -> String? {
            var error: NSError?
            // use ternary expression "? :"
            // if file exists return content else return nil
            return NSFileManager().fileExistsAtPath(path) ?
                String(contentsOfFile: path, encoding: utf8, error: &error)! :
            nil
    }
    // "class func" allows use of File.write(path, text) method call
    class func write(path: String, _ content: String, utf8: NSStringEncoding = NSUTF8StringEncoding) -> Bool {
        var error: NSError?
        // returns true on success
        return content.writeToFile(path, atomically: true, encoding: utf8, error: &error)
    }
}

// create text, file name and full file path
let mytext = "good morning everyone!"

let fname = "aatest.txt"

// full path (directory/fname)
let mypath = "\(NSHomeDirectory())/Documents/\(fname)"

// for testing ...
println(NSHomeDirectory())
println(mypath)

// try to write the file
if File.write(mypath, mytext) {
    println("file written")             // file written
} else {
    println("error writing file")
}

// try to read the file
if let mytext2 = File.read(mypath) {
    println(mytext2)                     // good morning everyone!
} else {
    println("error reading file")
}

// extra ...
if NSFileManager().fileExistsAtPath(mypath) {
    println("file \(mypath) exists!")
}