How to use AttributedString in UIKit

You might not know we can use AttributedString in UIKit. In this article, we will have a quick guide on how to do it.

AttributedString is a new struct for styling string introduced in iOS 15.

It lets us declare a string with associated attributes easily and more structurally.

Here is an example of creating an attributed string to work with a SwiftUI text view.

let string = "Attributed String"
var attributedString = AttributedString(string)
// 1
attributedString.foregroundColor = .pink
// 2
attributedString.font = .boldSystemFont(ofSize: 24)
// 3
attributedString.underlineStyle = .single

Text(attributedString)

1 Set font color.
2 Set font.
3 Set underline style.

As you can see, it is just a matter of creat a string and customizing its property.

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How to use AttributedString in UIKit

SwiftUI has a dedicated view for presenting text, Text, and it has a dedicated initializer that accept AttributedString.

Text.init(_ attributedContent: AttributedString)

For UIKit, it isn't that easy.

UIKit is an old framework with many ways to set strings based on UI components.

I classified it into two groups.

1. A view that accepts AttributedString.
2. A view that accepts NSAttributedString.

A view that accepts AttributedString

Apple adds support for AttributedString in some new APIs, such as UIButton.Configuration.

We can use AttributedString directly when using these new APIs.

var configuration = UIButton.Configuration.filled()
configuration.attributedTitle = AttributedString("Title")

A view that accepts NSAttributedString

There are only a few UIKit APIs that support AttributedString. So, most of the time, you must rely on the old NSAttributedString.

Luckily we can easily convert AttributedString to NSAttributedString.

To convert AttributedString to NSAttributedString, we use a new initializer of NSAttributedString. This initializer accepts AttributedString as an argument.

convenience init(_ attrStr: AttributedString)

This initializer acts as a bridge that allows us to use the new AttributedString with old UIKit APIs.

In this example, we convert AttributedString to NSAttributedString and assign it to UILabel.

let string = "Attributed String"
var attributedString = AttributedString(string)
attributedString.font = .boldSystemFont(ofSize: 40)
attributedString.foregroundColor = .systemPink
attributedString.underlineStyle = NSUnderlineStyle.single

let label = UILabel()
label.attributedText = NSAttributedString(attributedString)