Underline part of a string using NSMutableAttributedString in iOS 8 is not working

Question

I try to underline part of a string, for example, a 'string' part in 'test string' string. I'm using NSMutableAttributedString and my solution was working well on iOS7.

NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc]
        initWithString:@"test string"];
[attributedString addAttribute:NSUnderlineStyleAttributeName
                         value:@(NSUnderlineStyleSingle)
                         range:NSMakeRange(5, 6)];
myLabel.attributedText = attributedString;

The problem is that my solution is not working in iOS8 anymore. After spending an hour on testing multiple variants of NSMutableAttributedString, I found out that this solution works only when range starts with 0 (length can differ). What is the reason for that? How can I workaround this?

Solution 1

Update: By investigating this question: Displaying NSMutableAttributedString on iOS 8 I finally found the solution!

You should add NSUnderlineStyleNone at the beginning of the string.

Swift 4.2 (none was removed):

let attributedString = NSMutableAttributedString()
attributedString.append(NSAttributedString(string: "test ",
                                           attributes: [.underlineStyle: 0]))
attributedString.append(NSAttributedString(string: "s",
                                           attributes: [.underlineStyle: NSUnderlineStyle.single.rawValue]))
attributedString.append(NSAttributedString(string: "tring",
                                           attributes: [.underlineStyle: 0]))

Objective-C:

 NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] init];
 [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"test "
                                                                          attributes:@{NSUnderlineStyleAttributeName: @(NSUnderlineStyleNone)}]];
 [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"s"
                                                                         attributes:@{NSUnderlineStyleAttributeName: @(NSUnderlineStyleSingle),
                                                                                      NSBackgroundColorAttributeName: [UIColor clearColor]}]];
 [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"tring"]];

Another bonus of such approach is absence of any ranges. Very nice for localized strings.

Seems like it is Apple bug :(

Solution 2

I found that if you apply UnderlineStyleNone to the whole string you can then selectively apply underline to a part that starts in the middle:

func underlinedString(string: NSString, term: NSString) -> NSAttributedString {
    let output = NSMutableAttributedString(string: string)
    let underlineRange = string.rangeOfString(term)
    output.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.StyleNone.rawValue, range: NSMakeRange(0, string.length))
    output.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.StyleSingle.rawValue, range: underlineRange)

    return output
}

Solution 3

NSMutableAttributedString *signUpString = [[NSMutableAttributedString alloc] initWithString:@"Not a member yet?Sign Up now"];

[signUpString appendAttributedString:[[NSAttributedString alloc] initWithString:@" "attributes:@{NSUnderlineStyleAttributeName: @(NSUnderlineStyleNone)}]];

[signUpString addAttributes: @{NSForegroundColorAttributeName:UIColorFromRGB(0x43484B),NSUnderlineStyleAttributeName:[NSNumber numberWithInteger:NSUnderlineStyleSingle]} range:NSMakeRange(17,11)];

signUpLbl.attributedText = [signUpString copy];

It worked for me

Solution 4

It's September 2018, so this answer is not about iOS8 but it still relates to underlining part of a string.

Here is a Swift 4 extension that underlines a given term within an already composed myAttributedString

extension NSMutableAttributedString {

    func underline(term: String) {

        guard let underlineRange = string.range(of: term) else {

            return
        }

        let startPosition = string.distance(from: term.startIndex, to: underlineRange.lowerBound)
        let nsrange = NSRange(location: startPosition, length: term.count)

        addAttribute(
            .underlineStyle,
            value: NSUnderlineStyle.styleSingle.rawValue,
            range: nsrange)
    }
}

Usage: myAttributedString.underline(term: "some term")

Solution 5

Swift 5 version of @Joss's answer with few modifications, by adding a returned NSMutableAttributedString, because I couldn't use the original solution without it.

extension NSMutableAttributedString {

func underline(term: String) -> NSMutableAttributedString {
    guard let underlineRange = string.range(of: term) else {
        return NSMutableAttributedString()
    }
    let startPosition = string.distance(from: term.startIndex, to: underlineRange.lowerBound)
    let nsrange = NSRange(location: startPosition, length: term.count)
    addAttribute(
        .underlineStyle,
        value: NSUnderlineStyle.single.rawValue,
        range: nsrange)
    return self
    }   
}

Usage:

 let myUnderLinedText = "Hello World"
 let underLinedMutableString =  NSMutableAttributedString(string: myUnderLinedText, attributes: titleAttributes).underline(term: myUnderLinedText)

View more solutions

Comments

[KlimczakM]

I thought it was working, but unfortunately I ran the app in 7.1 simulator... Still not working on iOS8. But avoiding range is very nice, thanks!

[kelin]

To be honest, I didn't tested my code on iOS 8. But now I've done, and have finally found the solution.

[pvshnik]

Thanks. This really saved my time!

[H Raval]

how can remove underline after add

[H Raval]

how can remove underline after add

[kelin]

@HRaval, create a new string without underline.

[H Raval]

but how can i direct text is underlined or not?

[Jeremy Piednoel]

hey @kelin thanks for this answer. Just a small correction .underlineStyle: NSUnderlineStyle.single.rawValue,

[kelin]

@JeremyPiednoel, big thanks! Updated the answer for Swift 4.2.