9.32. Swift class

The Swift class is a generic and flexible construct used to build code.

We can define properties (constants, variables) and methods for the class.

Unlike other programming languages, Swift does not require you to create separate interfaces and implementation files for custom classes. All you have to do is define a class in a single file, and the system will automatically generate external interfaces for other code.

9.32.1. Comparison of classes and structures #

Classes and structures in Swift have a lot in common. What they have in common is:

Define properties to store values
Define methods to provide functionality
Define satellite scripts to access values
Define the constructor used to generate initialization values
Extend to add functionality implemented by default
Comply with the agreement to provide standard functionality for a class

Compared with structures, classes have the following additional functions:

Inheritance allows one class to inherit the characteristics of another class
Type conversion allows you to check and interpret the type of an instance ofa class at run time
The destructor allows a class instance to release any resources it is assigned
Reference counting allows multiple references to a class

9.32.2. Syntax: #

class classname { Definition 1 Definition 2 …… Definition N }

9.32.3. Class definition #

class student{ var studname: String var mark: Int var mark2: Int } 

Instantiate the class:

let studrecord = student() 

9.32.4. Example #

import Cocoa class MarksStruct { var mark: Int init(mark: Int) { self.mark = mark } } class studentMarks { var mark = 300 } let marks = studentMarks() print("The score is \(marks.mark)") 

The output of the above program execution is as follows:

The score is 300 

9.32.5. Access class properties as a reference type #

The properties of the class can be accessed through the . to visit. Theformat is: instantiate the class name. Attribute name:

import Cocoa class MarksStruct { var mark: Int init(mark: Int) { self.mark = mark } } class studentMarks { var mark1 = 300 var mark2 = 400 var mark3 = 900 } let marks = studentMarks() print("Mark1 is \(marks.mark1)") print("Mark2 is \(marks.mark2)") print("Mark3 is \(marks.mark3)") 

The output of the above program execution is as follows:

Mark1 is 300 Mark2 is 400 Mark3 is 900 

9.32.6. Identity operator #

Because a class is a reference type, it is possible for multiple constants and variables to reference a class instance at the same time in the background.

To determine whether two constants or variables refer to the same class instance, Swift has two identity operators built into it:

Identity operator	Unequal operator
The operator is: =	Operator is:! = =
Returns true if two constants or variables refer to the same class instance	Returns true if two constants or variables refer to different class instances

9.32.7. Example #

import Cocoa class SampleClass: Equatable { let myProperty: String init(s: String) { myProperty = s } } func ==(lhs: SampleClass, rhs: SampleClass) -> Bool { return lhs.myProperty == rhs.myProperty } let spClass1 = SampleClass(s: "Hello") let spClass2 = SampleClass(s: "Hello") if spClass1 === spClass2 {// false print("Referencing the same class instance \(spClass1)") } if spClass1 !== spClass2 {// true print("Referencing different class instances \(spClass2)") } 

The output of the above program execution is as follows:

Referencing different class instances SampleClass 