Is it possible to set custom font & size for NSString?

问题

I'm working with Swift in iOS 9. I want to customize the font for a UIAlertAction. I searched these questions for a Swift answer:

Change the Font of UIAlertAction in Swift

Is it possible to customize the font and appearance of a UIAlertController in the new XCode w/ iOS8?

And this question for an Objective-C answer: UIAlertController custom font, size, color

But there was no solution for customizing the font for a UIAlertAction.

I believe the problem is that a UIAlertAction uses an NSString for its title property. See demo project on Github.

I would like to create a string like so:

let originalString: String = "OK"
let myString: NSString = originalString as NSString

And then customize the string's font & size. Then after adding my actions to the alert controller, assign the string to my actions using key-value coding:

alertController!.actions[0].setValue(myString, forKey: "title")

But as far as I can tell, there is no way to set a custom font and size for an NSString. If it used a UILabel instead, then it would be easy to customize the font. But I seem to be stuck with the limitations of strings. Does anyone know a way to assign a custom font & size to a string, or am I correct in believing there is no way to do this?

回答1:

You would use NSAttributedString (or its mutable counterpart, NSMutableAttributedString) to make a string with custom info. As the constructor takes an NSString (or String in Swift), it will not take an NSAttributedString (NSAttributedString isn't a subclass of NSString.).

You could fudge the Swift compiler into passing an NSAttributedString using unsafeBitCast, but UIAlertAction may not like it.

---

Looking at UIAlertController custom font, size, color, it seems that you can set it using KVO. The code for doing of so is similar:

var alertVC = UIAlertController(title: "Dont care what goes here, since we're about to change below", message: "", preferredStyle: .ActionSheet)
let hogan = NSMutableAttributedString(string: "Presenting the great... Hulk Hogan!")
hogan.addAttribute(NSFontAttributeName, value: UIFont.systemFontOfSize(50), range: NSMakeRange(24, 11))

alertVC.setValue(hogan, forKey: "attributedTitle")

来源：https://stackoverflow.com/questions/33532941/is-it-possible-to-set-custom-font-size-for-nsstring