> On Oct 1, 2017, at 2:32 PM, Glenn L. Austin <gl...@austinsoft.com> wrote:
>
>>
>> On Oct 1, 2017, at 8:56 AM, Dave Reed via swift-users
>> <swift-users@swift.org> wrote:
>>
>>
>>> On Sep 21, 2017, at 3:58 PM, V T via swift-users <swift-users@swift.org>
>>> wrote:
>>>
>>> Hi there!
>>>
>>> Is there a best way to check if a given type conforms to numeric protocol
>>> (Integer or FP) at runtime?
>>>
>>> func checkNumeric<T>(_ value: T) {
>>> /* return true if vaiue is Integer or FP */
>>> /* this will not compile: */
>>> if value is Numeric {
>>>
>>> }
>>> }
>>>
>>> Best regards!
>>>
>>> VT
>>>
>>
>> I think the way to do it is to try casting as the type, but you can't use
>> "as? Numeric" as you get:
>>
>> error: protocol 'Numeric' can only be used as a generic constraint because
>> it has Self or associated type requirements
>>
>> but you could check for each specific numeric type such as:
>>
>> func checkNumeric<T>(_ value: T) {
>> if (value as? Int != nil) || (value as? Float != nil) {
>> print("numeric")
>> } else {
>> print("not numeric")
>> }
>> }
>>
>> checkNumeric(3)
>> checkNumeric(3.0)
>> checkNumeric("3")
>
> You can also use the 'is' operator, as in 'value is Int || value is Float ||
> value is Double'
>
> --
> Glenn L. Austin, Computer Wizard, AustinSoft.com
Ah, I had forgotten "is" works in Swift
Just be careful as:
func checkNumeric<T>(_ value: T) {
if (value is Int) || (value is Float) {
print("numeric")
} else {
print("not numeric")
}
}
checkNumeric(3)
checkNumeric(3.0)
checkNumeric("3")
outputs:
numeric
not numeric
not numeric
Since the literal 3.0 is a Double so you'd have to catch every floating point
type (including CGFloat, I suspect etc.) vs. just trying to cast to a Float
(although I guess casting to a Float could have unexpected results also if
someone made an extension that allows a type to be cast as a Float).
Dave
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