Swift4 Initialization

Swift Classes, structures and enumerations are used for preparing instance of a class once declared in Swift4. Initial value is initialized for stored property. The values are initialized to proceed further. The 'init()' method is used to create initialization function. Swift 4 initializer is different from Objective-C as it does not return any values. Its function is to check for initialization of newly created instances before its processing. Swift 4 also provides 'deinitialization' process for performing memory management operations once the instances are deallocated.

Initializer for Stored Properties

Stored properties have to initialize the instances for their classes and structures before processing the instances. Stored properties use initializer to assign and initialize values without need to call property observers.

To create an initial value.
To assign default property value within the property definition.
To initialize an instance for a particular data type 'init()' is used. No arguments are passed inside the init() function.

Syntax:

init() {
   //New Instance initialization goes here
}

Example

struct cube {
   var length: Double 
   var breadth: Double
   var height: Double
   init() {
      length = 6
      breadth = 12
      height = 4
   }
}
var volume = cube()
print("volume of cube is \(volume.length*volume.breadth*volume.height)")

Output:

volume of cube is 288.0

Here,

The structure "cube" is initialized with member length, breadth and height as "Double" datatype.
Init() method is used to initialize the values for the newly created members.
Volume of cube is calculated and returned by calling the cube function.

Setting Property Values by Default

In Swift4 programming language, the init() function is used to initialize the property values by default while declaring the class or structure members. When the property takes the same value alone throughout the program, we can declare it in the declaration section alone rather than initializing it in init(). Setting property values by default enables the user when inheritance is defined for classes or structures.

Example:

struct cube {
   var length = 6
   var breadth = 12
   var height = 4
}

var volume = cube()
print("volume of the cube is \(volume.length*volume.breadth*volume.height)")

Output:

volume of cube is 288

Parameter Initialization

In Swift4 language, the user can initialize parameters as part of the initializer's definition using init().

Example:

struct Rectangle {
   var length: Double
   var breadth: Double
   var area: Double
   init(fromLength length: Double, fromBreadth breadth: Double) {
      self.length = length
      self.breadth = breadth
      area = length * breadth
   }
   init(fromL l: Double, fromB b: Double) {
      self.length = l
      self.breadth = b
      area = l * b
   }
}
let a1 = Rectangle(fromLength: 6, fromBreadth: 12)
print("area is: \(a1.area)")

let a2 = Rectangle(fromL: 36, fromB: 12)
print("area is: \(a2.area)")

Output: