make part of the text bold in a UITextField - ios

Question

Based on the answers here I made this code:
extension NSMutableAttributedString {
func bold(text:String, size:CGFloat) -> NSMutableAttributedString {
let attrs:[String:AnyObject] = [NSFontAttributeName : UIFont.boldSystemFontOfSize(size)]
let boldString = NSMutableAttributedString(string:"\(text)", attributes:attrs)
self.appendAttributedString(boldString)
return self
}
func normal(text:String)->NSMutableAttributedString {
let normal = NSAttributedString(string: text)
self.appendAttributedString(normal)
return self
}
}
and I use it like this:
#IBOutlet weak var m_field: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
let string = NSMutableAttributedString()
string.bold("Bold_text: ",size: 12).normal("normal text")
m_field.attributedText = string
}
but it doesn't work, all my text is the same (bold I think)
what am I doing wrong?

Answer 1

Enjoy - below code works for swift 3
let normalText = "Hi am normal"
let boldText = "And I am BOLD!"
let attributedString = NSMutableAttributedString(string:normalText)
let attrs = [NSFontAttributeName : UIFont.boldSystemFont(ofSize: 15)]
let boldString = NSMutableAttributedString(string:boldText, attributes:attrs)
attributedString.append(boldString)
txt.attributedText = attributedString
where txt is TextField outlet

Answer 2

assign "**string**" variable value to **attributedText** property
var m_field = UITextField()
m_field.frame = CGRect(x: 0, y: 66, width: 400, height: 100)
let string = NSMutableAttributedString()
string.bold("Bold_text: ",size: 15).normal("normal text")
m_field.attributedText = string
self.view .addSubview(m_field)