iOS 10.3：如果将NSStrikethroughStyleAttributeName应用于NSMutableAttributedString的子范围，则不会渲染

Question

A strikethrough (single, double, ...) added as attribute to an instance of NSMutableAttributedString is not rendered if the apply range is not the whole string range.

This happens using addAttribute(_ name: String, value: Any, range: NSRange) , insert(_ attrString: NSAttributedString, at loc: Int) , append(_ attrString: NSAttributedString) , ...

Broken by Apple in early iOS 10.3 betas, and not fixed in 10.3 final.

Credit: https://openradar.appspot.com/31034683

Answer 1

Setting the baseline offset seems to fix it:

[attributedStr addAttribute:NSBaselineOffsetAttributeName value:@0 range:NSMakeRange(0, 10)];
[attributedStr addAttribute:NSStrikethroughStyleAttributeName value:@2 range:NSMakeRange(0, 10)];

This is a known bug in iOS 10.3

Answer 2

Adding a NSBaselineOffsetAttributeName , as explained here , to the attributed string brings back the strikethrough line. Overriding drawText:in: can be slow especially on Collection View or Table View Cells.

Answer 3

Found a workaround for our specific scenario (we don't specify any styling with UILabel's properties, but all with NSAttributedString attributes):

/// This UILabel subclass accomodates conditional fix for NSAttributedString rendering broken by Apple in iOS 10.3
final class PriceLabel: UILabel {

    override func drawText(in rect: CGRect) {
        guard let attributedText = attributedText else {
            super.drawText(in: rect)
            return
        }

        if #available(iOS 10.3, *) {
            attributedText.draw(in: rect)
        } else {
            super.drawText(in: rect)
        }
    }
}

NOTE: if you mix UILabel's styling properties with NSAttributedString attributes, you should think of creating a new attributed string before rendering, apply UILabel's styling on it and then re-apply all attributedText 's attributes over it.

Answer 4

swift 3 working code tested with 10.3

let attributeString: NSMutableAttributedString = NSMutableAttributedString(string: "₹3500")
attributeString.addAttribute(NSBaselineOffsetAttributeName, value: 0, range: NSMakeRange(0, attributeString.length))
attributeString.addAttribute(NSStrikethroughStyleAttributeName, value: 1, range: NSMakeRange(0, attributeString.length))
productPriceLabel.attributedText = attributeString

Answer 5

Swift 4

let text = "Hello World"
let textRange = NSMakeRange(0, text.count)
let attributedText = NSMutableAttributedString(string: text)
attributedText.addAttribute(NSAttributedStringKey.strikethroughStyle,
                            value: NSUnderlineStyle.styleSingle.rawValue,
                            range: textRange)
myLabel.attributedText = attributedText

Answer 6

Its a bug known to Xcode 8.3 (8E3004b) / iOS 10.3, with this workaround NO extra line of code is need, just add [NSBaselineOffsetAttributeName:0] when declaring NSMutableAttributedString()

let attrStr = NSMutableAttributedString(string: YOUR_STRING_HERE, attributes: [NSBaselineOffsetAttributeName : 0])

// Now if you add the strike-through attribute to a range, it will work
attrStr.addAttributes([
    NSFontAttributeName: UIFont.boldSystemFont(ofSize: 24),
    NSStrikethroughStyleAttributeName: 1
], range: NSRange)

Answer 7

对于Swift 5， NSBaselineOffsetAttributeName通过kCTBaselineOffsetAttributeName进行了更改，并将更改每个新版本。