Swift Properties

Properties are variables or constants that are associated with a class, structure, or enumeration in Swift. They define the data that objects of a type can store. Swift provides several types of properties, including stored properties, computed properties, and static properties, which allow developers to model data and behaviors effectively.

Basics of Properties

Properties in Swift are categorized into:

Stored Properties: Store constant or variable values as part of an instance.
Computed Properties: Do not store values directly but compute them dynamically.
Static Properties: Associated with the type itself rather than an instance.

Stored Properties

Stored properties store constant (let) or variable (var) values for instances of a class or structure.

Example: main.swift

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class Student {
  var name: String
  var age: Int
  
  init(name: String, age: Int) {
    self.name = name
    self.age = age
  }
}

let student = Student(name: "Arjun", age: 20)
print("Name: \(student.name), Age: \(student.age)")

Explanation:

name and age are stored properties of the Student class.
These properties are initialized via the initializer and accessed using the dot operator.

Output:

Computed Properties

Computed properties compute their value dynamically rather than storing it directly. They use get and optionally set blocks to define their behavior.

Example: main.swift

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class Rectangle {
  var width: Double
  var height: Double
  
  init(width: Double, height: Double) {
    self.width = width
    self.height = height
  }
  
  var area: Double {
    return width * height
  }
}

let rect = Rectangle(width: 5.0, height: 10.0)
print("Area: \(rect.area)")

Explanation:

area is a computed property that calculates the rectangle’s area using width and height.
It does not store the value but computes it each time it is accessed.

Output:

Getters and Setters for Computed Properties

Computed properties can have a set block to allow modification of their values.

Example: main.swift

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class Rectangle {
  var width: Double
  var height: Double
  
  init(width: Double, height: Double) {
    self.width = width
    self.height = height
  }
  
  var area: Double {
    get {
      return width * height
    }
    set {
      width = newValue / height
    }
  }
}

let rect = Rectangle(width: 5.0, height: 10.0)
print("Original Area: \(rect.area)")
rect.area = 100.0
print("New Width: \(rect.width)")

Explanation:

The get block calculates the area of the rectangle.
The set block adjusts the width based on the new area value.
newValue is a default parameter available in the set block.

Output:

Static Properties

Static properties belong to the type itself rather than any specific instance. They are defined using the static keyword.

Example: main.swift

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class Circle {
  static let pi = 3.14159
  var radius: Double
  
  init(radius: Double) {
    self.radius = radius
  }
  
  var circumference: Double {
    return 2 * Circle.pi * radius
  }
}

let circle = Circle(radius: 5.0)
print("Circumference: \(circle.circumference)")

Explanation:

pi is a static property shared by all instances of the Circle class.
It is accessed using the type name (Circle.pi).
The circumference property uses pi to calculate the circumference of the circle.

Output:

TutorialKart

Swift Properties