Static variable vs Class variable in Swift

How Static properties differs to usual properties ?

• Used to create type properties with either let or var. These are shared between all objects of a class. 
• During class loading time, a single memory location allocated for the property if we declared as static.
• Static property belongs to a class (or struct) Type rather than Instance of class (or struct). Hence it also called Type Properties

What if we declare "static var" ?

• Since it's a variable, we can change it in future even after initialised.
• When we change the value of the static variable property, that property is now changed in all future instances.

What if we declare "static let" ?

static let instance : Singleton = Singleton()

• Since it's constant, we cannot change once initialised. Its value will remain same even if we share among all the instance or object of a class or struct.
• Useful to adopt singleton pattern.

How class variables differ static variables ?

• It differ with the way it support inheritance. When you make a static property it becomes owned by the class and cannot be changed by subclasses, whereas when you use class it may be overridden if needed.

What if we declare "class var" or "class let" properties for example : 

class var realVariable: String = "Woo"

• We can't. Compiler error says 'class variable not yet supported!'
• Class variables are only supported in swift by way of Computed properties
• Hence we can declare :
• class var computed: String {
     return "Woo"
  }