Swift
"duration":"\(self.duration)" ] } }
var movie = film() movie.head = "Swift Properties" movie.duration = 3.09
println(movie.metaInfo["head"]!) println(movie.metaInfo["duration"]!) When we run the above program using playground, we get the following result: Swift Properties 3.09
Computed Properties as Property Observers In Swift to observe and respond to property values Property Observers are used. Each and every time when property values are set property observers are called. Except lazy stored properties we can add property observers to 'inherited' property by method 'overriding'. Property Observers can be defined by either
Before Storing the value - willset
After Storing the new value - didset
When a property is set in an initializer willset and didset observers cannot be called.
class Samplepgm { var counter: Int = 0{ willSet(newTotal){ println("Total Counter is: \(newTotal)") } didSet{ if counter > oldValue { println("Newly Added Counter \(counter - oldValue)") } } 111