Attributed string bullet points - Swift

gistfile1.swift

import UIKit
import PlaygroundSupport

struct StringConstants {
    static let bullet1 = "This is a small string."
    static let bullet2 = "This is more of medium string with a few more words etc."
    static let bullet3 = "Well this is certainly a longer string, with many more words than either of the previuos two strings."
}

typealias ParagraphData = (bullet: String, paragraph: String)

class MyViewController : UIViewController {
    private let label = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .white
        setupLabel()
        
        let paragraphDataPairs: [ParagraphData] = [
            ("▶︎ ", StringConstants.bullet1),
            ("▶︎ ", StringConstants.bullet2),
            ("\u{0009}▶︎ ", StringConstants.bullet1),
            ("\u{0009}▶︎ ", StringConstants.bullet2),
            ("\u{0009}▶︎ ", StringConstants.bullet3),
            ("▶︎ ", StringConstants.bullet3),
        ]

        let stringAttributes: [NSAttributedString.Key: Any] = [.font: label.font!]
        let bulletedAttributedString = makeBulletedAttributedString(paragraphDataPairs: paragraphDataPairs,
                                                                    attributes: stringAttributes)
        label.attributedText = bulletedAttributedString
    }
    
    private func makeBulletedAttributedString(paragraphDataPairs: [ParagraphData],
                                              attributes: [NSAttributedString.Key: Any]) -> NSAttributedString {
        let fullAttributedString = NSMutableAttributedString()
        
        paragraphDataPairs.forEach { paragraphData in
            let attributedString = makeBulletString(bullet: paragraphData.bullet,
                                                        content: paragraphData.paragraph,
                                                        attributes: attributes)
            fullAttributedString.append(attributedString)
        }
        
        return fullAttributedString
    }
    
    private func makeBulletString(bullet: String,
                                     content: String,
                                     attributes: [NSAttributedString.Key: Any]) -> NSAttributedString {
        let formattedString: String = "\(bullet)\(content)\n"
        let attributedString: NSMutableAttributedString = NSMutableAttributedString(string: formattedString,
                                                                                    attributes: attributes)
        
        let headerIndent = (bullet as NSString).size(withAttributes: attributes).width
        attributedString.addAttributes([.paragraphStyle: makeParagraphStyle(headIndent: headerIndent)],
                                       range: NSMakeRange(0, attributedString.length))
        return attributedString
    }
    
    private func makeParagraphStyle(headIndent: CGFloat) -> NSParagraphStyle {
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.firstLineHeadIndent = 0
        paragraphStyle.headIndent = headIndent

        return paragraphStyle
    }
    
    private func setupLabel() {
        view.addSubview(label)
        label.numberOfLines = 0
        label.font = UIFont.preferredFont(forTextStyle: .headline)
        
        label.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            label.topAnchor.constraint(equalTo: view.topAnchor, constant: 10),
            label.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 10),
            label.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -10),
        ])
    }
}

PlaygroundPage.current.liveView = MyViewController()