Lazy and Computed Properties

Hello,

In the previous lesson, we learned about stored properties. You can also define lazy and computed properties.

What I saw in the previous section was to store the data (Store) of stored properties.

Apart from that, we can define properties as computed and lazy.

Lazy Properties

When a property value will not need to be generated until the first time the property value is used, you can use a lazy stored property.

When a property value is not used until its first use, we can use it as a lazy stored property. Therefore, if the production of an object is costly and it is not necessary for the first time, we will pass the production of the object at the first use of that object and avoid unnecessary resource consumption and performance loss. In order to make a stored property a lazy stored property, we need to pass the lazy modifier.

class Person {
    lazy var name: String = "Name"
    var age:Int = 0
    private var _lastName:String = ""
    func profile() -> String {
        return "I'm \(self.name) and I'm \(self.age) years old."
    }

}

var p = Person()

p.name = "Coddy"
p.age = 10

print(p.profile())

Computed Properties

Computed properties receive an input and freeze the new result. In fact, he might think at first glance that it works like functions. However, computed properties are used with dot syntax just like properties.

In the example below, we can better understand the difference between the method and computed property.

In addition to stored properties, classes, structures, and enumerations can define computed properties, which do not actually store a value.

Instead, they provide a getter and an optional setter to retrieve and set other properties and values indirectly.

If you define get { } inside the property declaration, it makes that property to a computed property. And it cannot have initial value as when you access the property, it will always call get{} function declared in property.

class Person {
    lazy var name: String = "Name"
    var age:Int = 0
    private var _lastName:String = ""

    var lastName:String{
    get {
        return _lastName
    }
    set {
        _lastName = newValue
    }
    }

    var profile:String{
    get{
        return "I'm \(self.name) and I'm \(self.age) years old."
    }
    }

}

var p = Person()

p.name = "Matt"
p.age = 40


/*
Normally, if it was a method, we would call it with the p.profile () method.
However, since it is propery, it was enough to call it with .profile.
*/

p.profile

Congratulations 🎉

In this lesson, we learned Lazy and Computed Properties on Swift.

See you in the next lesson.