Swift computed property: what is it, how it work and when should you use it

Coming to this blog, our team – ArrowHiTech will introduce one of Swift’s  property styles called swift computed property. So are you ready? Let’s discover.

What is swift computed property?

A property is a value associate with  an object, like a class, struct or enum. It is as “sub-variables”. Deriving value from other properties is a popular use-case. We’ll create a filename based on the “name” and “file extension” in the example below:

Swift computed property

It is important that we could make this code simpler by removing the “return” keyword:

Swift computed property

Because the filename property is read-only, the following code would fail:

he filename property

You could make this more clear by adding the “get” wrapper around your computation:

“get” wrapper

How does swift computed property work?

A computed property swift usually defines a getter and can optionally have a setter. In short, a getter is the code to collect (“read”) a value from a property, whereas a setter is the code for setting (“write”) a property to a new value. 

Let’s see how getters and setters work for stored properties. 

Swift computed property

Getter – computed property swift

You will always provide a custom getter for a computed property when you create it. After all, you’re modifying the way the property provides a value – with a computation. Check out this computed property:


That’s exactly the same as this:


Besides that, the code that needs to execute to get/read a value from the area property with the get { ··· }code. Because a computed property at least returns a value, if you don’t provide the get { ··· } block, this getter is implied.

Setter – swift computed property

They control what happens when you change the value of a property. Here’s example:


In the code as you can see, In fact, you are free to name that value whatever you want! You can even leave out newValue entirely and still use it inside the setter. “newValue” is the setter’s “input.” When the code temp.fahrenheit = 86 is executed, the value 86 is available in the setter as newValue.

You can also see that the setter of a computed property, such as celcius, often involves another property. You cannot use the value of a property within its own getter or setter because this would result in an infinite loop.

When should I use a swift computed property?

It’s important to know when to use a computed property. You have to use this swift computed property in case:

  • It depends on other properties.
  • You’re defining a property within an extension.
  • The property provides access to another object without fully revealing it.


Swift computed property is a basic part in Swift. They can be used in a variety of ways, and it is important to understand the various use-cases. Our team also provides Mobile Application Development Services for you. So if you want to learn more about Swift, go to the Swift and object- C.iOS App Development Services.