Any way to bold part of a NSString?

Is there any way to bold only part of a string? For example:

>Approximate Distance: 120m away

Thanks!

What you could do is use an NSAttributedString.

NSString *boldFontName = [[UIFont boldSystemFontOfSize:12] fontName];
NSString *yourString = ...;
NSRange boldedRange = NSMakeRange(22, 4);

NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:yourString];

[attrString beginEditing];
[attrString addAttribute:kCTFontAttributeName 
                   value:boldFontName
                   range:boldedRange];

[attrString endEditing];
//draw attrString here...

Take a look at this handy dandy guide to drawing NSAttributedString objects with Core Text.

As Jacob mentioned, you probably want to use an NSAttributedString or an NSMutableAttributedString. The following is one example of how you might do this.

NSMutableAttributedString *string = [[NSMutableAttributedString alloc] initWithString:@"Approximate Distance: 120m away"];
NSRange selectedRange = NSMakeRange(22, 4); // 4 characters, starting at index 22

[string beginEditing];

[string addAttribute:NSFontAttributeName
           value:[NSFont fontWithName:@"Helvetica-Bold" size:12.0]
           range:selectedRange];

[string endEditing];

If you do not want to bother with fonts (as not every variation of font contains "Bold"), here is another way to do this. Please be aware, this is currently only available on OS X...:

NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:"Approximate Distance: 120m away"];
[attrString beginEditing];
[attrString applyFontTraits:NSBoldFontMask
                      range:NSMakeRange(22, 4)];
[attrString endEditing];

The code above gave me crash when I created UILabel with this attributedString.

I used this code and it worked:

NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:string];
NSRange boldedRange = NSMakeRange(0, 1);
UIFont *fontText = [UIFont systemFontOfSize:12]; //[UIFont fontWithName:@"Lato-Bold" size:12];
NSDictionary *dictBoldText = [NSDictionary dictionaryWithObjectsAndKeys:fontText, NSFontAttributeName, nil];
[attrString setAttributes:dictBoldText range:boldedRange];

Swift

Also includes getting the range of the string you want to embolden dynamically

let nameString = "Magoo"
let string = "Hello my name is \(nameString)"

let attributes = [NSFontAttributeName:UIFont.systemFontOfSize(14.0),NSForegroundColorAttributeName: UIColor.black]
let boldAttribute = [NSFontAttributeName:UIFont.boldSystemFontOfSize(14.0)]

let attributedString = NSMutableAttributedString(string: string, attributes: attributes)

let nsString = NSString(string: string)
let range = nsString.rangeOfString(nameString)

if range.length > 0 { attributedString.setAttributes(boldAttribute, range: range) }

someLabel.attributedText = attributedString

To bold a string without hardcoding its font, you can use the StrokeWidth attribute with a negative value:

let s = NSMutableAttributedString(string: "Approximate Distance: 120m away")
s.addAttribute(NSStrokeWidthAttributeName, value: NSNumber(value: -3.0), range: NSRange(22..<26))

An NSString is just a data container. It doesn't contain any details about presentation concerns.

It sounds like what you probably want to do is bold part of the UILabel that is being used to display your string. Which I don't think you can do. But you could always break the UI down into three labels, one for "Approximate Distance:", one for "120 m", and one for "away". Place them in-line with each other and you should get the desired effect.

Another option might be to use a UIWebView and a little bit of markup to display your string with embedded formatting information, as discussed here:

http://iphoneincubator.com/blog/windows-views/display-rich-text-using-a-uiwebview

In Xamarin ios you can bold part of a NSString this way:

public static NSMutableAttributedString BoldRangeOfString (string str, float fontSize, int startRange, int lengthRange)
	{
		var firstAttributes = new UIStringAttributes {
			Font = UIFont.BoldSystemFontOfSize(fontSize)
		};

		NSMutableAttributedString boldString = new NSMutableAttributedString (str);
		boldString.SetAttributes (firstAttributes.Dictionary, new NSRange (startRange, lengthRange));
		return boldString;
	}    

and call this method:

myLabel = new UILabel (); 
...
myLabel.AttributedText = BoldRangeOfString("my text", fontSize, startRange, lengthRange);    

I coupled @Jacob Relkin and @Andrew Marin answers, otherwise, I got the crashes. Here is the answer for iOS9:

UIFont *boldFont = [UIFont boldSystemFontOfSize:12];
NSString *yourString = @"Approximate Distance: 120m away";
NSRange boldedRange = NSMakeRange(22, 4);

NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:yourString];

[attrString beginEditing];
[attrString addAttribute:NSFontAttributeName 
                   value:boldFont
                   range:boldedRange];

[attrString endEditing];

I took a look at the official documentation: 1 and 2.

Shorter way using Swift5+

let labelNotes = UILabel()  //or UITextView(), etc...
let attributedNotes = NSMutableAttributedString(string: "Bold: some stuff not bold")
attributedNotes.addAttribute(NSAttributedString.Key.font, value: UIFont.boldSystemFont(ofSize: 14), range: NSRange(location: 0, length: 5))
labelNotes.attributedText = attributedNotes

If you don't want to hardcode the font or/and the size try this code for bolding full strings:

NSMutableAttributedString *myString = [[NSMutableAttributedString alloc] initWithString:mainString];
[myString beginEditing];
[myString addAttribute:NSStrokeWidthAttributeName
                         value:[[NSNumber alloc] initWithInt: -3.f]
                         range:NSMakeRange(0, [mainString length])];
[myString endEditing];