[swift-evolution] Thoughts on "Fully eliminate implicit bridging conversions from Swift"

[Charlie Monroe]

What error do you get (i.e. why doesn't it compile)?

Have you tried this?

let result: [String : AnyObject] = [
	"inputImage": [
		kCIAttributeIdentity: 0,
		kCIAttributeClass: "CIImage",
		kCIAttributeDisplayName: "Image",
		kCIAttributeType: kCIAttributeTypeScalar
	]
]
return result

Charlie

> On May 24, 2016, at 6:07 PM, simon gladman via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Apologies for arriving a little late to the party and I hope this is a suitable forum to discuss this subject. I've spent some time over the last few days moving a large Core Image project to Swift 3.0 and come across some side effects which I think are related to proposal SE-0072, Fully eliminate implicit bridging conversions from Swift.
> 
> First off, rightly or wrongly, I've always typed the scalar parameters of my subclassed CIFilters as CGFloat. It makes working with CIVectors and CGRects cleaner and feels more "Swifty" than using NSNumber. However, moving to Swift 3.0, using anything apart from an NSNumber breaks. For example:
> 
>         let radius: CGFloat = 25
>         
>         let blur = CIFilter(
>             name: "CIGaussianBlur",
>             withInputParameters: [kCIInputRadiusKey: radius])
> 
> The same with passing arguments to a CIKernel, CIWarpKernel or CIColorKernel:
> 
>         kernel.apply(
>             withExtent: CGRect(x: 0, y: 0, width: 100, height: 100),
>             arguments: [radius])
> 
> Secondly, the attributes property of a filter (of type [String: AnyObject]) which I'd normally code along the lines of:
> 
>     override var attributes: [String : AnyObject]
>     {
>         return [
>             "inputImage": [
>                  kCIAttributeIdentity: 0,
>                  kCIAttributeClass: "CIImage",
>                  kCIAttributeDisplayName: "Image",
>                  kCIAttributeType: kCIAttributeTypeScalar]
>         ]
>     }
> 
> ...fails to compile. kCIAttributeTypeScalar is of type String and needs to be cast to NSString and the dictionary itself needs to be cast to AnyObject:
> 
>     override var attributes: [String : AnyObject]
>     {
>         return [
>             "inputImage": [
>                  kCIAttributeIdentity: 0,
>                  kCIAttributeClass: "CIImage",
>                  kCIAttributeDisplayName: "Image",
>                  kCIAttributeType: kCIAttributeTypeScalar as NSString] as AnyObject
>         ]
>     }
> 
> It seems awkward to me that the constant supplied by Core Image to describe an attribute's type needs to be cast to another type to get it working. 
> 
> Are these changes just something that we'll need to live with? Are they still in flux? Have I totally misunderstood everything and there's a more elegant solution?
> 
> Any thoughts would be greatly appreciated!
> 
> Simon
> 
> 
> Simon Gladman     +44 7973 669691 <tel:%2B44%207973%20669691>
> 
> Blog: http://flexmonkey.blogspot.co.uk <http://flexmonkey.blogspot.co.uk/>
> GitHub: https://github.com/FlexMonkey <https://github.com/FlexMonkey>
> Twitter: @FlexMonkey <https://twitter.com/FlexMonkey>
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