Re: Generics Question
Re: Generics Question
- Subject: Re: Generics Question
- From: Michael de Haan <email@hidden>
- Date: Sun, 26 Jul 2015 15:49:53 -0700
Oops… I should have called it genericTfor etc as in:
>>>>>>>>>>>>>>>
func intFor(s:String) -> Int {
return Int(s)!
}
func genericTFor<T>(s:String) -> T {
return T(s)!
}
let intFromStr = intFor("9")
let intFromStrB:Double = genericTFor("9")
<<<<<<<<<<<<<<<<
in other words, write a generic function that will return an Int, Double for a given string value, depending upon the input i.e. T
> On Jul 26, 2015, at 3:44 PM, Alan Westbrook <email@hidden> wrote:
>
> I think you want genericIntFor() to return Int instead of T
>
> Alan
>
>> On Jul 26, 2015, at 3:10 PM, Michael de Haan <email@hidden> wrote:
>>
>> I’m writing a coreData helper which will rely on Generics.
>>
>> Could I get some input?
>>
>> I have synthesized the problem down to this somewhat nonsensical code.
>>
>> From Playground:
>>
>>
>>>>>>>>>>
>>
>>
>> func intFor(s:String) -> Int {
>>
>> return Int(s)!
>>
>> }
>>
>> func genericIntFor<T>(s:String) -> T {
>>
>> return T(s)! // T cannot be constructed because it has no accessible initializers.
>>
>> }
>>
>>
>>
>> let intFromStr = intFor("9”) // 9
>> let intFromStrB:Double = genericIntFor("9”)
>>
>> <<<<<<<<<
>>
>>
>>
>> The first function does pretty much what it says.
>> The second tries to use Generics, with an error as shown. Now, I **thought** ( which is often not a good thing) that T would allow , in this case, either an integer or double to be returned, given a valid string input that represents a number, say from 0 to 9.
>> Is it possible the way I wrote, or is there some fundamental misunderstanding of Generics? Thanks in advance.
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