Hi Chris,
Can you file a radar or JIRA for us on this? It looks like something should be
fixed in the documentation at least, or perhaps in the bridging.
- Tony
> On Nov 11, 2016, at 1:46 PM, Chris Anderson via swift-users
> <swift-users@swift.org> wrote:
>
> I'm having problems with the type conversion between a Swift `Decimal` and an
> Objective C `NSDecimalNumber`.
>
> If I have the Swift class:
>
> @objc class Exam: NSObject {
> var grade: Decimal = 90.0
> }
>
> And try to use that Swift class in Objective C,
>
> Exam *exam = [[Exam alloc] init];
> NSDecimalNumber *result = [[NSDecimalNumber zero]
> decimalNumberByAdding:grade.value];
>
> I get the error:
>
> Sending 'NSDecimal' to parameter of incompatible type 'NSDecimalNumber *
> _Nonnull'
>
> as it seems like `grade` is being treated as an `NSDecimal` not an
> `NSDecimalNumber`. This seems incorrect as per
> https://developer.apple.com/reference/foundation/nsdecimalnumber
> <https://developer.apple.com/reference/foundation/nsdecimalnumber> it says
>
> "The Swift overlay to the Foundation framework provides the Decimal
> structure, which bridges to the NSDecimalNumber class. The Decimal value type
> offers the same functionality as the NSDecimalNumber reference type, and the
> two can be used interchangeably in Swift code that interacts with Objective-C
> APIs. This behavior is similar to how Swift bridges standard string, numeric,
> and collection types to their corresponding Foundation classes."
>
> So I'm not sure if 1) I'm doing something wrong. 2) there's an error in the
> documentation or 3) this is a Swift bug. Number 1 on that list is definitely
> the most likely, but I wanted to see what I’m missing here.
>
> I don't want to explicitly make the values in my Swift class
> `NSDecimalNumber` because then I cannot do simple arithmetic operations such
> as `+` without doing the whole ugly `decimalNumberByAdding` dance.
>
> Thanks for the help!
>
> Best,
> Chris Anderson
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