Swift numerics and CGFloat (CGPoint, CGRect, etc.)

Question

I\'m finding Swift numerics particularly clumsy when, as so often happens in real life, I have to communicate with Cocoa Touch with regard to CGRect and CGPoint (e.g., becau

Answer 1

Explicitly typing scale to CGFloat, as you have discovered, is indeed the way handle the typing issue in swift. For reference for others:

let scale: CGFloat = 2.0
let r = self.view.bounds
var r2 = CGRect()
r2.size.width = r.width * scale

Not sure how to answer your second question, you may want to post it separately with a different title.

Update:

Swift creator and lead developer Chris Lattner had this to say on this issue on the Apple Developer Forum on July 4th, 2014:

What is happening here is that CGFloat is a typealias for either Float or Double depending on whether you're building for 32 or 64-bits. This is exactly how Objective-C works, but is problematic in Swift because Swift doesn't allow implicit conversions.

We're aware of this problem and consider it to be serious: we are evaluating several different solutions right now and will roll one out in a later beta. As you notice, you can cope with this today by casting to Double. This is inelegant but effective :-)

Update In Xcode 6 Beta 5:

A CGFloat can be constructed from any Integer type (including the sized integer types) and vice-versa. (17670817)

Answer 2

I wrote a library that handles operator overloading to allow interaction between Int, CGFloat and Double.

https://github.com/seivan/ScalarArithmetic

As of Beta 5, here's a list of things that you currently can't do with vanilla Swift. https://github.com/seivan/ScalarArithmetic#sample

I suggest running the test suite with and without ScalarArithmetic just to see what's going on.

Answer 3

I created an extension for Double and Int that adds a computed CGFloatValue property to them.

extension Double {
    var CGFloatValue: CGFloat {
        get {
            return CGFloat(self)
        }
    }
}
extension Int {
    var CGFloatValue: CGFloat {
        get {
            return CGFloat(self)
        }
    }
}

You would access it by using let someCGFloat = someDoubleOrInt.CGFloatValue

Also, as for your CGRect Initializer, you get the missing argument labels error because you have left off the labels, you need CGRect(x: d, y: d, width: d, height: d) you can't leave the labels out unless there is only one argument.