Object Oriented Programming
Inheritance in Swift
Inheritance is used to inherit another class' members, including fields and methods. A subclass extends a base class' members.
Syntax
modifier class subClass: baseClass {
//the initializer is NOT inherited by default
override init() {
super.init()
}
//to access a superClass member
super.methodName();
//to override a superClass member, use the override keyword
override superClassMember() {
}
} ;Notes
The super keyword is used to access the super class' member.
When a method is overridden, the compiler checks to see if the same method declaration exists in the super class. Override can be prevented using the 'final' keyword.
Example
public class Cat {
var name: String
init() {
this.name = "Garfield";
}
func sound() -> String { //implemented sound method from the interface
return "Meow!";
}
}
public class Tiger: Cat { //the variable 'name' and the method 'sound()' are inherited
init() {
super.init(); //calling the constructor in the super class, Cat
}
override func sound() -> String { //overriding the sound() method in Cat
return "Roar!";
}
func catSound() -> String {
return super.sound(); //calling the sound method from Cat, non-overwritten
}
}