AttributedString Builder

A simple way to build up attributed strings using result builders from a variety of sources. Based on the episodes from Swift Talk.

Plain strings
Markdown
Images
SwiftUI Views
Table support
PDF export

Here's an example showing plain strings, Markdown and SwiftUI views:

@AttributedStringBuilder
var example: some AttributedStringConvertible {
    "Hello, World!"
        .bold()
        .modify { $0.backgroundColor = .yellow }
    """
    This is some markdown with **strong** `code` text. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas tempus, tortor eu maximus gravida, ante diam fermentum magna, in gravida ex tellus ac purus.

    - One
    - Two
    - Three

    > A blockquote.
    """.markdown()
    Embed {
        HStack {
            Image(systemName: "hand.wave")
                .font(.largeTitle)
            Text("Hello from SwiftUI")
            Color.red.frame(width: 100, height: 50)
        }
    }

You can then turn this example into a multi-page PDF like this:

let data = await example
    .joined(separator: "\n") // join the parts using newlines
    .run(environment: .init(attributes: sampleAttributes)) // turn into a single `NSAttributedString`
    .pdf() // render as PDF
try! data.write(to: .desktopDirectory.appending(component: "out.pdf"))

Here's a larger sample.

Features

Attributes

The Attributes struct is a value type representing the attributes in an NSAttributedString. During the building of the attributed string, this is passed on through the environment.

Strings

You can turn any string directly into an attributed string. The attributes from the environment are used to do this. You can also modify the environment in a way very similar to what SwiftUI does. For example, you can write "Hello".bold()" to take the current attributes, make them bold, and then render the string "Hello"` using these modified attributes.

Markdown

You can take any Markdown string and render it into an attributed string as well. For most customization, you can pass in a custom stylesheet.

Images

You can embed any NSImage into the attributed string, they're rendered as-is.

SwiftUI Views

SwiftUI views can be embedded using the Embed modifier. By default, it proposes nil⨉nil to the view, but this can be customized. SwiftUI views are rendered into a PDF context and are embedded as vector graphics.

Tables

You can construct tables in attributed strings using the Table support. This interface might still change (ideally, we'd use result builders for this as well).

Environment

You can use the environment in a way similar to SwiftUI's Environment to pass values down the view tree.

wildthink / attributed-string-builder