Using slugified and style-based tags in SwiftUI

Aug 19, 2022 · Follow on Twitter and Mastodon swiftuiopen-sourcetagging

As I’m rewriting an old app from scratch, I’m adding content tagging to it. For reusability, I’ve put all tag-specific logic in a new library called TagKit. Let’s take a look!

TagKit logotype

How to slugify strings

One common way to handle tags is to slugify their names, which is removing unsupported characters from a string and replacing any whitespaces with a separator.

You can see slugified strings in many web urls (for instance this one), where the page date and title is often slugified to create a unique valid url that also describes the content.

I wrote about slugifying strings in this blog post earlier this year. I use this logic in TagKit, but made it a little more configurable when creating it as a reusable package.

In TagKit, the Slugifiable protocol describes a slugifyable type:

public protocol Slugifiable {

    var slugifiableValue: String { get }

String implements this protocol by default, by returning itself as the slugifiable value.

Once a type implements Slugifiable, it can be slugified with the slugified() function:

let string = "Hello, world!"
let slug = string.slugified() // Returns "hello-world"

You can also provide a custom SlugConfiguration to customize the slugified result:

let string = "Hello, world!"
let config = SlugConfiguration(
    separator: "+",
    allowedCharacters: NSCharacterSet(charactersIn: "hewo")
let slug = string.slugified(configuration: config) // Returns "he+wo"

You probably won’t need to use these functions directly, nor customize the configuration, but you can if you want or need to.

Taggable types

With slugification in place, let’s implement tagging, which can be used to group, filter, etc.

In TagKit, the Taggable protocol describes a taggable type:

public protocol Taggable {

    var tags: [String] { get set }

Once a type implements Taggable, it can use all the functionality the protocol provides, such as hasTags, hasTag(...), addTag(...), removeTag(...), toggleTag(...), etc.

This means that you can now let your domain model and observable types implement Taggable and automatically get access to a bunch of logic.


TagKit has views to make it easier to work with tags. For instance, TagList let you list and edit tags, TagCapsule renders a tag, and TagTextField slugifies text as you type.

An animated gif of an app that uses TagKit

The image above shows very plain tag capsules, but you can style these capsules in any way you like, or even replace them with your own custom views.


TagKit is small library, but I like how creating these small, focused packages makes it easy to reuse functionality and share what you create. If you try it out, I hope you like it.

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