After implementing the proposal
https://github.com/apple/swift-evolution/blob/master/proposals/0170-nsnumber_bridge.md
<https://github.com/apple/swift-evolution/blob/master/proposals/0170-nsnumber_bridge.md>
we have gotten some initial feedback.
It seems that there is definitely a fair amount of confusion and heartache for
dealing with Float and Double values being bridged.
Specifically the cases like:
NSNumber(value 0.1) as? Float
which with the current implementation will return nil since the Double value
0.1 cannot be represented exactly as a Float.
It seems like the overwhelming majority of users know full well that Float will
result in a loss of precision (hence why they chose that type over Double).
This means that the floating point bridges for Double, Float, and CGFloat
should not be the pedantic “exactly” cases but instead infer the conversion
intent of a lax/approximated version.
So in short: for the betterment of the API ergonomics, the floating point types
as destinations will be pulled back to their initial Swift 3 behavior.
Additionally to aide appropriate migration to the appropriate
truncating/exactly initializers the un-labeled, deprecated in Swift 4, plain
init methods to the numeric types with an NSNumber will now be annotated with
the suggested replacements.
Thanks for your time and feedback,
Philippe Hausler
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