learn about willSet and didSet, explore the class methods parameters usage

swift_learn_04.swift

//willSet and didSet 
class Shape{
    var oldName :String
    var newName :String
    var name :String{
        willSet{
            self.oldName=name
            self.newName=newValue
            println("WillSet: old values is \(name), new values is \(newValue)")
        }
        
        didSet{
            println("DidSet: old value is \(oldValue), new values is \(name))")
        }
    }
    init(name:String){
        self.name=name
        self.newName=""
        self.oldName=""
    }
    
    func desc(){
        println("my name is \(self.name)")
    }
}

var s1=Shape(name:"jemy")
s1.desc()

s1.name="orange"
s1.desc()

//class methods
class Counter{
    var count :Int = 0
    func incBy(amount :Int, numberOfTimes times:Int){
        self.count += amount * times
    }
    
    func incBy2(amount :Int, times:Int)
    {
        self.count += amount * times
    }
    
    func incBy3(amount :Int, times :Int?)
    {
        var innerTimes=1
        if times != nil{
            innerTimes=Int((times?.value)!)
        }
        self.count += amount * innerTimes
    }
}

var counter = Counter()
counter.incBy(2, numberOfTimes: 7)
println(counter.count)
counter.incBy(2, numberOfTimes: 10)
println(counter.count)
counter.incBy2(10, times: 10)
println(counter.count)

counter.incBy3(100, times: nil)
println(counter.count)