Making text bold using attributed string in swift

Here is a neat way to make a combination of bold and normal texts in a single label.

Extension:

Swift 3.0

extension NSMutableAttributedString {
    @discardableResult func bold(_ text:String) -> NSMutableAttributedString {
        let attrs:[String:AnyObject] = [NSFontAttributeName: UIFont(name: "AvenirNext-Medium", size: 12)!]
        let boldString = NSMutableAttributedString(string: text, attributes:attrs)
        self.append(boldString)
        return self
    }

    @discardableResult func normal(_ text:String)->NSMutableAttributedString {
        let normal =  NSAttributedString(string: text)
        self.append(normal)
        return self
    }
}

Swift 4

extension NSMutableAttributedString {
    @discardableResult func bold(_ text: String) -> NSMutableAttributedString {
        let attrs: [NSAttributedStringKey: Any] = [.font: UIFont(name: "AvenirNext-Medium", size: 12)!]
        let boldString = NSMutableAttributedString(string:text, attributes: attrs)
        append(boldString)

        return self
    }

    @discardableResult func normal(_ text: String) -> NSMutableAttributedString {
        let normal = NSAttributedString(string: text)
        append(normal)

        return self
    }
}

Usage:

let formattedString = NSMutableAttributedString()
formattedString
    .bold("Bold Text")
    .normal(" Normal Text ")
    .bold("Bold Text")

let lbl = UILabel()
lbl.attributedText = formattedString

Result:

Bold Text Normal Text Bold Text

var normalText = "Hi am normal"

var boldText  = "And I am BOLD!"

var attributedString = NSMutableAttributedString(string:normalText)

var attrs = [NSFontAttributeName : 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 8.3.2 • Swift 3.1

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:

extension String {
    var html2AttStr: NSAttributedString? {
        return try? NSAttributedString(data: Data(utf8), options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: 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
Ian

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

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)
Samuel

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)
    }
}

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
}
J.S.R - Silicornio

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
    }
}

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

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)!
}

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

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"

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

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
        }
    }