static or the class modifier?

Junior PRO

The idea

Both keywords declare a member of the type, not of an instance. The difference is overriding:

• static — the member cannot be overridden in a subclass. The only option for struct, enum, protocols and for stored type properties.
• class — classes only; the member can be overriden in a subclass. Allowed for methods, computed properties and subscripts, but not for stored properties.

Inside a class static is equivalent to final class.

class Shape {
    static let kind = "shape"             // cannot be overridden
    class var name: String { "Shape" }    // can be overridden
    static func make() -> Shape { Shape() }
    // class var stored = 0   // error: class stored properties not supported
}
class Circle: Shape {
    override class var name: String { "Circle" }
    // override static func make() — error: cannot override static method
}
struct Point {
    static let zero = Point(x: 0, y: 0)   // struct/enum: static only
    var x, y: Double
}
print(Circle.name, Shape.name, Shape.kind)   // Circle Shape shape