UILabel and UITextView add line spacing

1-protocols.swift

import UIKit

protocol LabelLineSpacingable where Self: UILabel {
    func lineSpacing(_ value: CGFloat)
}

protocol TextViewLineSpacingable where Self: UITextView {
    func lineSpacing(_ value: CGFloat,
                     content: String,
                     withColor color: UIColor?,
                     withFontSize fontSize: CGFloat?)
}

extension LabelLineSpacingable {
    func lineSpacing(_ spacingValue: CGFloat) {
        // MARK: - Check if there's any text

        guard let textString = text else { return }

        // MARK: - Create "NSMutableAttributedString" with your text

        let attributedString = NSMutableAttributedString(string: textString)

        // MARK: - Create instance of "NSMutableParagraphStyle"

        let paragraphStyle = NSMutableParagraphStyle()

        // MARK: - Actually adding spacing we need to ParagraphStyle

        paragraphStyle.lineSpacing = spacingValue
        paragraphStyle.lineBreakMode = .byTruncatingTail

        // MARK: - Adding ParagraphStyle to your attributed String

        attributedString.addAttribute(
            .paragraphStyle,
            value: paragraphStyle,
            range: NSRange(location: 0, length: attributedString.length))

        // MARK: - Assign string that you've modified to current attributed Text

        attributedText = attributedString
    }
}

extension TextViewLineSpacingable {
    func lineSpacing(_ value: CGFloat, content: String, withColor color: UIColor?, withFontSize fontSize: CGFloat?) {
        let style = NSMutableParagraphStyle()
        style.lineSpacing = value
        style.alignment = .left

        let color = color ?? .white
        let fontSize = fontSize ?? 16

        attributedText = NSAttributedString(string: content,
                                            attributes: [
                                                .paragraphStyle: style,
                                                .foregroundColor: color,
                                                .font: UIFont.systemFont(ofSize: fontSize)
                                            ])
    }
}

2-extensions.swift

import UIKit

extension UILabel: LabelLineSpacingable {}
extension UITextView: TextViewLineSpacingable {}

3-HowToUse.md

How to use

// UILabel
label.lineSpacing(8)

// UITextView
textView.lineSpacing(10, content: "demo demo demo", withColor: .white, withFontSize: 16)