NSFontAttributeName vs NSAttributedStringKey.font

Question

I am having some trouble with Swift code in a library I have been using for a while. It seems related to some kind of version conflict, but I am not sure.

Here is the code:

let attribMsg = NSAttributedString(string: msg,
                               attributes: [NSAttributedStringKey.font:UIFont.systemFont(ofSize: 23.0)])

Here is the error message I get from the compiler:

Type 'NSAttributedStringKey' (aka 'NSString') has no member 'font'
    Did you mean 'zone'?  Fix(button)

Using this code in different project I noticed that on some of them I do not get the error message and it all compiles without any problem.

I also noticed that if I replace the above code by the following:

let attribMsg = NSAttributedString(string: msg,
                               attributes: [NSFontAttributeName:UIFont.systemFont(ofSize: 23.0)])

The projects with a problem will work while the others(previously working) show this other message:

'NSFontAttributeName' has been renamed to 'NSAttributedStringKey.font'

In other words some projects work with one type of code and some others work with the other type.

Needless to say that I do not want to change the code each time I switch from one project to another.

The experiments I made changing the Deployment Target of the project do not seem to make much difference. So comes my question: What is the way to handle this issue?

Answer 1

The projects are probably in different versions of Swift.

In Swift 4, NSFontAttributeName has been replaced with NSAttributedStringKey.font.

In Swift 5, NSFontAttributeName has been replaced with NSAttributedString.Key.font.