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)