AttributedString.swift

//
//  ViewController.swift
//  Font
//
//  Created by Bob on 2019/7/9.
//  Copyright © 2019 Hamster. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var tv: UITextView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        let attr = NSAttributedString()
        
        tv.attributedText = attr.appendLine(text: "Somebody said:")
                                .appendBullet(text: "An apple a day")
                                .appendBullet(text: "Keep doctor away")
    }

}


extension NSAttributedString {
    
    @discardableResult
    func appendBullet(text: String, bulletSymbol: String = "\u{2022}", bulletColor: UIColor = .black) -> NSAttributedString {
        let font = UIFont.systemFont(ofSize: 30)
        let indentation: CGFloat = 20
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.tabStops = [ NSTextTab(textAlignment: .left, location: indentation) ]
        paragraphStyle.defaultTabInterval = indentation
        paragraphStyle.headIndent = indentation
        let bulletText = "\(bulletSymbol)\t" + "\(text)\n"
        let bulletStyleModifier: [NSAttributedString.Key:Any] = [.font: font, .paragraphStyle: paragraphStyle]
        let tmp = NSMutableAttributedString(attributedString: self)
        tmp.append(NSAttributedString(string: bulletText))
        tmp.addAttributes([.foregroundColor: bulletColor], range: NSRange(location: self.length, length: bulletSymbol.count))
        tmp.addAttributes(bulletStyleModifier, range: NSRange(location: self.length, length: bulletText.count))
        return tmp
    }
    
    @discardableResult
    func appendLine(text: String, color: UIColor = .red) -> NSAttributedString {
        let font = UIFont.systemFont(ofSize: 30)
        let modifier: [NSAttributedString.Key:Any] = [.font: font, .foregroundColor: color]
        let willAppendString = text + "\n"
        let tmp = NSMutableAttributedString(attributedString: self)
        tmp.append(NSAttributedString(string: willAppendString))
        tmp.addAttributes(modifier, range: NSRange(location: self.length, length: text.count))
        return tmp
    }
    
    
}