从 HTML 暗模式初始化的 NSAttributedString，如何设置默认前景色？

Question

While converting an existing app to dark mode I stumbled across an initialisation of an UITextView with an NSAttributedString to supply the fine print for some app store legalese. This looks fine in light mode, but in dark mode I get black text on black. My first idea to supply a default foreground color was to add this:

import UIKit

let fgColor: UIColor
if #available(iOS 13.0, *) {
    fgColor = .label
} else {
    fgColor = .black
}
let s = try NSAttributedString(data: NSLocalizedString("""
        <p style="text-align: center; font-size: smaller;">
        Your payment will be charged to your iTunes Account at confirmation of purchase. Your subscription automatically renews unless auto-renew is turned off at least 24-hours before the end of the current period. Your Account will be charged for renewal within 24-hours prior to the end of the current period at the same price as the original subscription.
        </p>
        <p style="text-align: center; font-weight: bold; font-size: smaller;">
        <a href="https://www.example.com/tos.html">Terms of Service</a>&nbsp;&vert;&nbsp;<a href="https://www.example.com/policy.html">Privacy Policy</a>
        </p>
""", comment: "legalese").data(using: String.Encoding.utf8, allowLossyConversion: false)!,
                               options: [.documentType: NSAttributedString.DocumentType.html.rawValue,
                                         .defaultAttributes: [NSAttributedString.Key.foregroundColor: fgColor]],
                               documentAttributes: nil)

But whatever I tried, I can not change the default foreground color. Any ideas?

Answer 1

I have tried to create an extension.

Here, data is the HTML data that I want to convert to Attributed String, "appLabelBlueColor" and "appSystemSecondaryColor" are the system colors that I want to reflect in Dark Mode.

var htmlToAttributedString: NSAttributedString? {   
guard let data = data(using: .utf16,allowLossyConversion: true)
else { return NSAttributedString() }

 do {
        let attributedString = try NSMutableAttributedString(data: data, options: [NSAttributedString.DocumentReadingOptionKey.documentType:  NSAttributedString.DocumentType.html], documentAttributes: nil)
        attrbutedString.addAttributes([NSAttributedString.Key.font:UIFont.systemFont(ofSize: 10, weight: .light), NSAttributedString.Key.foregroundColor: UIColor(named: "appLabelBlueColor")!, NSAttributedString.Key.backgroundColor: UIColor(named: "appSystemSecondaryColor")!], range: NSRange(
                                            location: 0,
                                            length: attribitedString.length))
        return attributedString

    } catch
    {
        return NSAttributedString()
    }
}

Usage:

cell.detailLabel.attributedText = mfPerformanceTableObjectModel[indexPath.section].contentText.htmlToAttributedString