basic class definition and function override

swift_learn_03.swift

//define a class

class Shape{
    var name :String
    var numberOfSlides = 0
    let pi :Float = 3.14
    
    init(name :String){
        self.name=name
    }
    
    deinit{
        //something you want to do before the class object is dead
    }
    
    func simpleDesc() -> String{
        return "A shape called \(self.name) with \(self.numberOfSlides) slides"
    }
    
    func circleArea(radius:Float) -> Float{
        return self.pi * radius * radius
    }
    
    func rectangleArea(width :Float, height :Float) -> Float{
        return width * height
    }
}

var c1=Shape(name:"circle number 1")
c1.circleArea(10)

var r1=Shape(name:"rectange number 1")
r1.numberOfSlides=4
var r1Area=r1.rectangleArea(100, height: 12)
println(r1.simpleDesc())
println("r1 area \(r1Area)")


//overwrite a class
class RawShape{
    let pi :Float = 3.14
    var name :String
    init(name:String){
        self.name=name
    }
    
    func area()->Float{
        return 0
    }
    
    func desc()->String{
        return "this is a shape called \(name)"
    }
}

class Circle : RawShape{
    var radius :Float
    init(radius :Float, name :String){
        self.radius=radius
        super.init(name:name)
    }
    
    override func area() -> Float {
        return pi * radius * radius
    }
    
    override func desc() -> String {
        return "this is cicle called \(self.name)"
    }
}

var c2 = Circle(radius: 10, name: "CIR1")
println(c2.area())
println(c2.desc())
c2.name="CIR BIG"
c2.radius=135
println(c2.area())
println(c2.desc())

class Rectange : RawShape {
    var width :Float
    var height :Float
 
    init(width :Float, height: Float, name :String){
            self.width=width
            self.height=height
            super.init(name: name)
    }
    
    var areaVal :Float{
        get{return self.width * self.height}
        //explicit name for newValue
        set(newAreaVal){
            self.areaVal = newAreaVal
        }
    }
    
    override func area()->Float{
        return self.width * self.height
    }
}

var r2 = Rectange(width:10,height:20,name:"BIG RECT")
println(r2.area())
println(r2.areaVal)
println(r2.desc())