9.36. Swift inheritance

Inheritance can be understood as one class getting the methods and properties of another class.

When a class inherits other classes, the inherited class is called a subclass, and the inherited class is called a superclass (or parent class).

In Swift, classes can call and access superclass methods, properties, and subscript scripts, and can override them.

We can also add a property watcher to the inherited properties in the class.

9.36.1. Base class #

A class that does not inherit another class is called a Base Class.

In the following example, we define the base class StudDetails describing the student (stname) and his scores in each subject (mark1, mark2, mark3):

class StudDetails { var stname: String! var mark1: Int! var mark2: Int! var mark3: Int! init(stname: String, mark1: Int, mark2: Int, mark3: Int) { self.stname = stname self.mark1 = mark1 self.mark2 = mark2 self.mark3 = mark3 } } let stname = "swift" let mark1 = 98 let mark2 = 89 let mark3 = 76 let sds = StudDetails(stname:stname, mark1:mark1, mark2:mark2, mark3:mark3); print(sds.stname) print(sds.mark1) print(sds.mark2) print(sds.mark3) 

The output of the above program execution is as follows:

swift 98 89 76 

9.36.2. Subclass #

A subclass refers to creating a new class based on an existing class.

To indicate the superclass of a class, write the superclass name after the subclass name, separated by a colon (:). The syntax format is as follows

class SomeClass: SomeSuperclass { // Class definition } 

Example

In the following example, we define a superclass StudDetails and then use the subclass Tom inherit it:

class StudDetails { var mark1: Int; var mark2: Int; init(stm1:Int, results stm2:Int) { mark1 = stm1; mark2 = stm2; } func show() { print("Mark1:\(self.mark1), Mark2:\(self.mark2)") } } class Tom : StudDetails { init() { super.init(stm1: 93, results: 89) } } let tom = Tom() tom.show() 

The output of the above program execution is as follows:

Mark1:93, Mark2:89 