Making text bold using attributed string in swift

I have a string like this

var str = "@text1 this is good @text1"

Now replace text1 with another string, say t 1. I am able to replace the text, but i am not able to bold it. I want to bold the new string t 1, so that the final output will be:

@t 1 this is good @t 1

How can I do it?

All the examples I am seeing are in Objective-C, but I want to do it in Swift.

Thanks in advance.

Usage:

let label = UILabel()
label.attributedText =
    NSMutableAttributedString()
        .bold("Address: ")
        .normal(" Kathmandu, Nepal\n\n")
        .orangeHighlight(" Email: ")
        .blackHighlight(" [email protected] ")
        .bold("\n\nCopyright: ")
        .underlined(" All rights reserved. 2020.")

Result:

Here is a neat way to make a combination of bold and normal texts in a single label plus some other bonus methods.

Extension: Swift 5.*

extension NSMutableAttributedString {
    var fontSize:CGFloat { return 14 }
    var boldFont:UIFont { return UIFont(name: "AvenirNext-Bold", size: fontSize) ?? UIFont.boldSystemFont(ofSize: fontSize) }
    var normalFont:UIFont { return UIFont(name: "AvenirNext-Regular", size: fontSize) ?? UIFont.systemFont(ofSize: fontSize)}
    
    func bold(_ value:String) -> NSMutableAttributedString {
        
        let attributes:[NSAttributedString.Key : Any] = [
            .font : boldFont
        ]
        
        self.append(NSAttributedString(string: value, attributes:attributes))
        return self
    }
    
    func normal(_ value:String) -> NSMutableAttributedString {
        
        let attributes:[NSAttributedString.Key : Any] = [
            .font : normalFont,
        ]
        
        self.append(NSAttributedString(string: value, attributes:attributes))
        return self
    }
    /* Other styling methods */
    func orangeHighlight(_ value:String) -> NSMutableAttributedString {
        
        let attributes:[NSAttributedString.Key : Any] = [
            .font :  normalFont,
            .foregroundColor : UIColor.white,
            .backgroundColor : UIColor.orange
        ]
        
        self.append(NSAttributedString(string: value, attributes:attributes))
        return self
    }
    
    func blackHighlight(_ value:String) -> NSMutableAttributedString {
        
        let attributes:[NSAttributedString.Key : Any] = [
            .font :  normalFont,
            .foregroundColor : UIColor.white,
            .backgroundColor : UIColor.black
            
        ]
        
        self.append(NSAttributedString(string: value, attributes:attributes))
        return self
    }
    
    func underlined(_ value:String) -> NSMutableAttributedString {
        
        let attributes:[NSAttributedString.Key : Any] = [
            .font :  normalFont,
            .underlineStyle : NSUnderlineStyle.single.rawValue
            
        ]
        
        self.append(NSAttributedString(string: value, attributes:attributes))
        return self
    }
}

Note: If compiler is missing UIFont/UIColor, replace them with NSFont/NSColor.

var normalText = "Hi am normal"

var boldText  = "And I am BOLD!"

var attributedString = NSMutableAttributedString(string:normalText)

var attrs = [NSAttributedString.Key.font : UIFont.boldSystemFont(ofSize: 15)]
var boldString = NSMutableAttributedString(string: boldText, attributes:attrs)

attributedString.append(boldString)

When you want to assign it to a label:

yourLabel.attributedText = attributedString

edit/update: Xcode 13.1 • Swift 5.5.1

If you know HTML and CSS you can use it to easily control the font style, color and size of your attributed string as follow:

>Discussion
The HTML importer should not be called from a background thread (that is, the options dictionary includes documentType with a value of html). It will try to synchronize with the main thread, fail, and time out. Calling it from the main thread works (but can still time out if the HTML contains references to external resources, which should be avoided at all costs). The HTML import mechanism is meant for implementing something like markdown (that is, text styles, colors, and so on), not for general HTML import.

---

extension StringProtocol {
    var html2AttStr: NSAttributedString? {
        try? NSAttributedString(data: Data(utf8), options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil)

    }
}

---

"<style type=\"text/css\">#red{color:#F00}#green{color:#0F0}#blue{color: #00F; font-weight: Bold; font-size: 32}</style><span id=\"red\" >Red,</span><span id=\"green\" > Green </span><span id=\"blue\">and Blue</span>".html2AttStr

If you're working with localised strings, you might not be able to rely on the bold string always being at the end of the sentence. If this is the case then the following works well:

e.g. Query "blah" does not match any items

/* Create the search query part of the text, e.g. "blah". 
   The variable 'text' is just the value entered by  the user. */
let searchQuery = "\"\(text)\""

/* Put the search text into the message */
let message = "Query \(searchQuery). does not match any items"

/* Find the position of the search string. Cast to NSString as we want
   range to be of type NSRange, not Swift's Range<Index> */
let range = (message as NSString).rangeOfString(searchQuery)

/* Make the text at the given range bold. Rather than hard-coding a text size,
   Use the text size configured in Interface Builder. */
let attributedString = NSMutableAttributedString(string: message)
attributedString.addAttribute(NSFontAttributeName, value: UIFont.boldSystemFontOfSize(label.font.pointSize), range: range)

/* Put the text in a label */
label.attributedText = attributedString

This is the best way that I have come up with. Add a function you can call from anywhere and add it to a file without a class like Constants.swift and then you can embolden words within any string, on numerous occasions by calling just ONE LINE of code:

To go in a constants.swift file:

import Foundation
import UIKit

func addBoldText(fullString: NSString, boldPartOfString: NSString, font: UIFont!, boldFont: UIFont!) -> NSAttributedString {
   let nonBoldFontAttribute = [NSFontAttributeName:font!]
   let boldFontAttribute = [NSFontAttributeName:boldFont!]
   let boldString = NSMutableAttributedString(string: fullString as String, attributes:nonBoldFontAttribute)
   boldString.addAttributes(boldFontAttribute, range: fullString.rangeOfString(boldPartOfString as String))
   return boldString
}

Then you can just call this one line of code for any UILabel:

self.UILabel.attributedText = addBoldText("Check again in 30 DAYS to find more friends", boldPartOfString: "30 DAYS", font: normalFont!, boldFont: boldSearchFont!)


//Mark: Albeit that you've had to define these somewhere:

let normalFont = UIFont(name: "INSERT FONT NAME", size: 15)
let boldFont = UIFont(name: "INSERT BOLD FONT", size: 15)

I extended David West's great answer so that you can input a string and tell it all the substrings you would like to embolden:

func addBoldText(fullString: NSString, boldPartsOfString: Array<NSString>, font: UIFont!, boldFont: UIFont!) -> NSAttributedString {
    let nonBoldFontAttribute = [NSFontAttributeName:font!]
    let boldFontAttribute = [NSFontAttributeName:boldFont!]
    let boldString = NSMutableAttributedString(string: fullString as String, attributes:nonBoldFontAttribute)
    for i in 0 ..< boldPartsOfString.count {
        boldString.addAttributes(boldFontAttribute, range: fullString.rangeOfString(boldPartsOfString[i] as String))
    }
    return boldString
}

And then call it like this:

let normalFont = UIFont(name: "Dosis-Medium", size: 18)
let boldSearchFont = UIFont(name: "Dosis-Bold", size: 18)
self.UILabel.attributedText = addBoldText("Check again in 30 days to find more friends", boldPartsOfString: ["Check", "30 days", "find", "friends"], font: normalFont!, boldFont: boldSearchFont!)

This will embolden all the substrings you want bolded in your given string

Swift 4 and higher

For Swift 4 and higher that is a good way:

    let attributsBold = [NSAttributedString.Key.font : UIFont.systemFont(ofSize: 16, weight: .bold)]
    let attributsNormal = [NSAttributedString.Key.font : UIFont.systemFont(ofSize: 16, weight: .regular)]
    var attributedString = NSMutableAttributedString(string: "Hi ", attributes:attributsNormal)
    let boldStringPart = NSMutableAttributedString(string: "John", attributes:attributsBold)
    attributedString.append(boldStringPart)
  
    yourLabel.attributedText = attributedString

In the Label the Text looks like: "Hi John"

Building on Jeremy Bader and David West's excellent answers, a Swift 3 extension:

extension String {
    func withBoldText(boldPartsOfString: Array<NSString>, font: UIFont!, boldFont: UIFont!) -> NSAttributedString {
        let nonBoldFontAttribute = [NSFontAttributeName:font!]
        let boldFontAttribute = [NSFontAttributeName:boldFont!]
        let boldString = NSMutableAttributedString(string: self as String, attributes:nonBoldFontAttribute)
        for i in 0 ..< boldPartsOfString.count {
            boldString.addAttributes(boldFontAttribute, range: (self as NSString).range(of: boldPartsOfString[i] as String))
        }
        return boldString
    }
}

Usage:

let label = UILabel()
let font = UIFont(name: "AvenirNext-Italic", size: 24)!
let boldFont = UIFont(name: "AvenirNext-BoldItalic", size: 24)!
label.attributedText = "Make sure your face is\nbrightly and evenly lit".withBoldText(
    boldPartsOfString: ["brightly", "evenly"], font: font, boldFont: boldFont)

usage....

let attrString = NSMutableAttributedString()
            .appendWith(weight: .semibold, "almost bold")
            .appendWith(color: .white, weight: .bold, " white and bold")
            .appendWith(color: .black, ofSize: 18.0, " big black")

two cents...

extension NSMutableAttributedString {
    
    @discardableResult func appendWith(color: UIColor = UIColor.darkText, weight: UIFont.Weight = .regular, ofSize: CGFloat = 12.0, _ text: String) -> NSMutableAttributedString{
        let attrText = NSAttributedString.makeWith(color: color, weight: weight, ofSize:ofSize, text)
        self.append(attrText)
        return self
    }
    
}
extension NSAttributedString {
   
    public static func makeWith(color: UIColor = UIColor.darkText, weight: UIFont.Weight = .regular, ofSize: CGFloat = 12.0, _ text: String) -> NSMutableAttributedString {
        
        let attrs = [NSAttributedStringKey.font: UIFont.systemFont(ofSize: ofSize, weight: weight), NSAttributedStringKey.foregroundColor: color]
        return NSMutableAttributedString(string: text, attributes:attrs)
    }
}

Accepting as valid the response of Prajeet Shrestha in this thread, I would like to extend his solution using the Label if it is known and the traits of the font.

Swift 4

extension NSMutableAttributedString {
    
    @discardableResult func normal(_ text: String) -> NSMutableAttributedString {
        let normal = NSAttributedString(string: text)
        append(normal)
        
        return self
    }
    
    @discardableResult func bold(_ text: String, withLabel label: UILabel) -> NSMutableAttributedString {
            
        //generate the bold font
        var font: UIFont = UIFont(name: label.font.fontName , size: label.font.pointSize)!
        font = UIFont(descriptor: font.fontDescriptor.withSymbolicTraits(.traitBold) ?? font.fontDescriptor, size: font.pointSize)
        
        //generate attributes
        let attrs: [NSAttributedStringKey: Any] = [NSAttributedStringKey.font: font]
        let boldString = NSMutableAttributedString(string:text, attributes: attrs)
        
        //append the attributed text
        append(boldString)
        
        return self
    }
}

For -> Search Television by size

1-way using NString and its Range

let query = "Television"
let headerTitle = "size"
let message = "Search \(query) by \(headerTitle)"
let range = (message as NSString).range(of: query)
let attributedString = NSMutableAttributedString(string: message)
attributedString.addAttribute(NSAttributedString.Key.font, value: UIFont.boldSystemFont(ofSize: label1.font.pointSize), range: range)
label1.attributedText = attributedString

another without using NString and its Range

let query = "Television"
let headerTitle = "size"
let (searchText, byText) = ("Search ", " by \(headerTitle)")
let attributedString = NSMutableAttributedString(string: searchText)
let byTextAttributedString = NSMutableAttributedString(string: byText)
let attrs = [NSAttributedString.Key.font : UIFont.boldSystemFont(ofSize: label1.font.pointSize)]
let boldString = NSMutableAttributedString(string: query, attributes:attrs)
attributedString.append(boldString)
attributedString.append(byTextAttributedString)
label1.attributedText = attributedString

swift5

Super easy way to do this.

    let text = "This string is having multiple font"
    let attributedText = 
    NSMutableAttributedString.getAttributedString(fromString: text)

    attributedText.apply(font: UIFont.boldSystemFont(ofSize: 24), subString: 
    "This")

    attributedText.apply(font: UIFont.boldSystemFont(ofSize: 24), onRange: 
    NSMakeRange(5, 6))

For more detail click here: https://github.com/iOSTechHub/AttributedString

This could be useful

class func createAttributedStringFrom (string1 : String ,strin2 : String, attributes1 : Dictionary<String, NSObject>, attributes2 : Dictionary<String, NSObject>) -> NSAttributedString{

let fullStringNormal = (string1 + strin2) as NSString
let attributedFullString = NSMutableAttributedString(string: fullStringNormal as String)

attributedFullString.addAttributes(attributes1, range: fullStringNormal.rangeOfString(string1))
attributedFullString.addAttributes(attributes2, range: fullStringNormal.rangeOfString(strin2))
return attributedFullString
}

Swift 3.0

Convert html to string and font change as per your requirement.

do {
       
     let str = try NSAttributedString(data: ("I'm a normal text and <b>this is my bold part . </b>And I'm again in the normal text".data(using: String.Encoding.unicode, allowLossyConversion: true)!), options: [ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil)
        
     myLabel.attributedText = str
     myLabel.font =  MONTSERRAT_BOLD(23)
     myLabel.textAlignment = NSTextAlignment.left
} catch {
     print(error)
}

func MONTSERRAT_BOLD(_ size: CGFloat) -> UIFont
{
    return UIFont(name: "MONTSERRAT-BOLD", size: size)!
}

Swift 5.1 use NSAttributedString.Key instead of NSAttributedStringKey

let test1Attributes:[NSAttributedString.Key: Any] = [.font : UIFont(name: "CircularStd-Book", size: 14)!]
let test2Attributes:[NSAttributedString.Key: Any] = [.font : UIFont(name: "CircularStd-Bold", size: 16)!]

let test1 = NSAttributedString(string: "\(greeting!) ", attributes:test1Attributes)
let test2 = NSAttributedString(string: firstName!, attributes:test2Attributes)
let text = NSMutableAttributedString()

text.append(test1)
text.append(test2)
return text

Just use code something like this:

 let font = UIFont(name: "Your-Font-Name", size: 10.0)!
        
        let attributedText = NSMutableAttributedString(attributedString: noteLabel.attributedText!)
        let boldedRange = NSRange(attributedText.string.range(of: "Note:")!, in: attributedText.string)
        attributedText.addAttributes([NSAttributedString.Key.font : font], range: boldedRange)
        noteLabel.attributedText = attributedText

two liner in swift 4:

            button.setAttributedTitle(.init(string: "My text", attributes: [.font: UIFont.systemFont(ofSize: 20, weight: .bold)]), for: .selected)
            button.setAttributedTitle(.init(string: "My text", attributes: [.font: UIFont.systemFont(ofSize: 20, weight: .regular)]), for: .normal)

Improving upon Prajeet Shrestha answer : -

You can make a generic extension for NSMutableAttributedString which involves less code. In this case I have chosen to use system font but you could adapt it so you can input the font name as a parameter.

    extension NSMutableAttributedString {

        func systemFontWith(text: String, size: CGFloat, weight: CGFloat) -> NSMutableAttributedString {
            let attributes: [String: AnyObject] = [NSFontAttributeName: UIFont.systemFont(ofSize: size, weight: weight)]
            let string = NSMutableAttributedString(string: text, attributes: attributes)
            self.append(string)
            return self
        }
    }

You can do this using simple custom method written below. You have give whole string in first parameter and text to be bold in the second parameter. Hope this will help.

func getAttributedBoldString(str : String, boldTxt : String) -> NSMutableAttributedString {
        let attrStr = NSMutableAttributedString.init(string: str)
        let boldedRange = NSRange(str.range(of: boldTxt)!, in: str)
        attrStr.addAttributes([NSAttributedString.Key.font : UIFont.systemFont(ofSize: 17, weight: .bold)], range: boldedRange)
        return attrStr
    }

usage: initalString = I am a Boy

label.attributedText = getAttributedBoldString(str : initalString, boldTxt : "Boy")

resultant string = I am a Boy