In Swift, a constructor is used to initialize an object of a class. Constructors are created using the init() method, which is called when a new instance of the class is created.
Here are some examples:
### Basic constructor
class Person {
var name: String
var age: Int
init(name: String, age: Int) {
self.name = name
self.age = age
}
}
let person1 = Person(name: "John", age: 25)
print(person1.name) // Output: John
print(person1.age) // Output: 25
In the above code, we have created a Person class that has a name and age property. We have also created a constructor that takes two parameters name and age, and initializes the object with these values.
### Default constructor
class Person {
var name: String
var age: Int
init() {
self.name = "Unknown"
self.age = 0
}
}
let person2 = Person()
print(person2.name) // Output: Unknown
print(person2.age) // Output: 0
In the above code, we have created a default constructor for the Person class, which initializes the name and age properties to default values.
### Convenience constructor
class Person {
var name: String
var age: Int
init(name: String, age: Int) {
self.name = name
self.age = age
}
convenience init(name: String) {
self.init(name: name, age: 0)
}
}
let person3 = Person(name: "Susan")
print(person3.name) // Output: Susan
print(person3.age) // Output: 0
In the above code, we have created a convenience constructor for the Person class, which initializes the name property and sets the age property to 0. It calls the primary constructor using self.init() with the age value set to 0.
We can create as many constructors as needed for a class to support different initialization scenarios.