Adding NSMutableAttributedString into a TextField

Question

I have a custom UITextfield which I want when the user finishes typing, a small "R$" must be added at the begging of the text with different size.

I call the method to add the "R$" like this:

self.addTarget(self, action: #selector(setCurrencyLabelPosition), for: .editingDidEnd)

and then I try to change the attributes and content like this:

 func setCurrencyLabelPosition(){

        let fullText:String = "R$\((self.text)!)"
        self.text = fullText
        var attribute:NSMutableAttributedString = NSMutableAttributedString(attributedString:self.attributedText!)
        attribute.addAttribute(NSFontAttributeName, value:UIFont.systemFont(ofSize: 12), range: NSRange(location:  0, length: 2))
        self.attributedText = attribute

    }

the original text of this textfield is set for size 40.0, I want only the "R$" to be of size 12.0

The problem I'm facing is that the whole text gets the size 40.0 It prints the "R$" but the size of 40.

Is it possible to do what I'm trying to using NSMutableAttributedString?

Answer 1

I had been working on your question, I think there is a bug in UITextField because if you modify the font to bigger font it works but if you do so but for small font then don't work.

I have done a custom class and added some customizable Inspectable properties, hope this finally help you

This is how looks, Note: the glitch is because of my gif converter

import UIKit

@IBDesignable
class CustomTextField: UITextField {

    @IBInspectable var prefix : String = ""
    @IBInspectable var removePrefixOnEditing : Bool = true

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func awakeFromNib() {
        super.awakeFromNib()
        self.addTarget(self, action: #selector(setCurrencyLabelPosition), for: .editingDidEnd)
        self.addTarget(self, action: #selector(removePrefix), for: .editingDidBegin)
    }

    func removePrefix(){
        if self.attributedText != nil
        {
            if(self.removePrefixOnEditing)
            {
                self.defaultTextAttributes = [NSFontAttributeName : UIFont.systemFont(ofSize: 20)]
                let prefixRange = NSString(string: (self.attributedText?.string)!).range(of: prefix)
                if(prefixRange.location != NSNotFound)
                {
                    self.attributedText = NSAttributedString(string: (self.attributedText?.string.replacingOccurrences(of: prefix, with: ""))!, attributes: self.defaultTextAttributes)
                }
            }
        }
    }

    func setCurrencyLabelPosition(){

        if self.attributedText != nil
        {
            var fullText:String = "\((self.attributedText?.string)!)"
            if(NSString(string: (self.attributedText?.string)!).range(of: prefix).location == NSNotFound)
            {
                fullText = "\(prefix)\((self.attributedText?.string)!)"
            }
            //hacky part, seems to be a bug in UITextField
            self.defaultTextAttributes = [NSFontAttributeName : UIFont.systemFont(ofSize: 10)]
            self.attributedText = NSAttributedString(attributedString: self.changeFontForText(originalText: fullText, text: prefix, basicFont: UIFont.systemFont(ofSize: 20), newFont: UIFont.systemFont(ofSize: 12)))
        }
    }

    func changeFontForText(originalText:String,text:String,basicFont:UIFont, newFont:UIFont) -> NSMutableAttributedString
    {
        let resultAttributedString = NSMutableAttributedString(string: originalText, attributes: [NSFontAttributeName : basicFont])
        let range = NSString(string: originalText).range(of: text)
        if(range.location != NSNotFound)
        {
            resultAttributedString.setAttributes([NSFontAttributeName:newFont], range: range)
        }

        return resultAttributedString
    }

}

Hope this helps