iOS 15.0 / macOS 12.0 / tvOS 15.0 / watchOS 8.0

iOS 15 comes with markdown string support. By default, you can style your strings with standard markdown syntax like **bold** and *italic* This is nice, but there is usually a need to specify more complex styling like font type, text color etc.

StyledMarkdown is a mini library that lets you define custom styles in code and use those styles in your localized markdown strings.

• Define your custom styles in code via specifying attributes like custom fonts, text colors, underline styles and more, and name those syles.
• Use those style names in your markdown strings.
• Provide your custom style definitions and markdown strings which are using those custom styles' names to StyledMarkdown. StyledMarkdown can create SwiftUI Text views or just AttributedStrings for UIKit.

With this approach, you do not have to define a custom AttributedStringKey each time you want a custom style in your markdown, as StyledMarkdown handles this part for you.

let normalStyle = Style { style in
	style.font = .subheadline
	style.foregroundColor = .red
}

let boldStyle = Style { style in
	style.font = Font.italic(.system(size: 20))()
	style.foregroundColor = .blue
}

let myStyleGroup = StyleGroup(
	base: normalStyle,
	[
		"bold": boldStyle
	]
)

Text(
	"Hey ^[buddy](style: 'bold')",
	styleGroup: myStyleGroup
)

// or

AttributedString(
	localized: "Hey ^[buddy](style: 'bold')",
	styleGroup: myStyleGroup
)

The idea of StyleGroup and named Styles comes directly from SwiftRichString library by Daniele Margutti on GitHub. Some of the code from there is also used in this package.

let rainbow: [Color] = [
	.blue, .teal, .red, .gray, .yellow, .orange, .purple
]

let rainbowStyleGroup = StyleGroup(
	styleCustom: { source in
		var attrString = source
		for run in attrString.runs {
			let currentRange = run.range
			var index = currentRange.lowerBound
			var colorCounter: Int = 0
			while index < currentRange.upperBound {
				let nextIndex = attrString.characters.index(
					index,
					offsetBy: 1
					)
				attrString[index ..< nextIndex].foregroundColor = rainbow[colorCounter]
				colorCounter += 1
				if colorCounter >= rainbow.count {
					colorCounter = 0
				}
				index = nextIndex
			}
		}
		return attrString
	}
)

Text(
	"Rainbow",
	styleGroup: rainbowStyleGroup
)

// or

AttributedString(
	localized: "Rainbow",
	styleGroup: rainbowStyleGroup
)

Parts of the above code for rainbow styling is taken from WWDC'21 sample app project called Caffe, Copyright © 2021 Apple Inc.

You can add links inside your strings using the custom link AttributedStringKey: ^[styled link](link: {url: 'http://www.example.com', style: 'linkStyle'})

Automatic grammar agreement's inflect property works with StyledMarkdown styles.

^[2 salad](style: 'italic', inflect: true)

generates 2 salads with italic style.

iOS currently does not support including custom Image attachments within AttributedString.