Set parts of text to different alpha values

Question

I'm writing an app that shows a list of items in a table view. You can tap each item in the table view to get a popup (via a standard UIAlertController) to get more information about that item.

One thing I'd like to include is ratings on a couple of different scales — so for example, if the rating is 3/5 cars, it would say Car Rating: . But I feel it would be better if the user knew this was a rating out of 5, which I could accomplish by adding two more "grayed-out" car emojis (i.e., alpha = 0.3), similar to the way Amazon would show 4 filled stars and 1 empty star for an item with a 4-star rating out of 5.

Then the question is: is there any way to set the alpha value of some of the text in the alert to 0.3 while the rest is 1 (I've done my research and can't find anything, so it looks like no)? If not, any recommended workarounds? Thanks!

Answer 1

If you want to apply different alpha values for text, you could make use of the attributed text as follows,

Instead of assigning text value assign the text to attributedText value as in the following example,

// MARK: - Different text style in alertController

@IBAction func buttonPressed(_ sender: Any) {
    // Sample attributed text
    let attributedText = applyDifferentStyle(forString: "Hello", inString: "Hello world")

    // Alert controller
    let alertController = UIAlertController(title: "Attributed texts example", message: nil, preferredStyle: .alert)

    // OK button in alert
    let okButton = UIAlertAction(title: "OK", style: .default, handler: nil)
    alertController.addAction(okButton)

    // Assign attributed text
    alertController.setValue(attributedText, forKey: "attributedMessage")

    // Show alert
    present(alertController, animated: true, completion: nil)
}

func applyDifferentStyle(forString: String, inString: String) -> NSMutableAttributedString {
    // Let your color be as follows with the alpha value as you wanted
    let greenColour = UIColor(red: 10/255, green: 190/255, blue: 50/255, alpha: 0.7)
    let redColor = UIColor.red

    // create the attribute as you want
    let customAttribute = [NSAttributedStringKey.foregroundColor : greenColour];

    // Other normal text attribute
    let normalTextAttributes = [NSAttributedStringKey.foregroundColor : redColor]

    let attString:NSMutableAttributedString = NSMutableAttributedString(string: inString
        , attributes: normalTextAttributes)

    // Apply attribute to texts
    let stringRange = (inString as NSString).range(of: forString)
    attString.setAttributes(customAttribute, range: stringRange)

    return attString
}

Simple demo project reference:
https://github.com/bharath-dev/StackoverflowSolutions/tree/master/AttributedAlertText