[swift-users] How do generics interact with overloaded methods?

[Wallacy]

Generics are compile time feature, but like said, not like c++ templates.
Unconstrained generic T will be like Any. " return self.myBar.read()" can
only be translated to a "function pointer" to the generic version, because
is the only information available at compile time.
Has a talk on wwdc explaining this.
Swift can do generic specialization, but only when information enough to do
this. Usually constrained generic is the way to go.


Em qui, 14 de jan de 2016 às 05:05, Ryan Conway via swift-users <
swift-users at swift.org> escreveu:

> Hey swift-users,
>
> I'm teaching myself Swift, coming from a mostly C and Python background,
> and would like to understand generics more deeply. Right now, I'm seeing
> generic data types invoke overloaded methods in ways I do not understand,
> and am seeking clarification why.
>
> In an effort to model a data structure whose data can be represented as
> multiple data types simultaneously, I've made this class. Here its
> implementation is mocked using constants.
>
> class Bar {
>     func read() -> Int {
>         return -1
>     }
>     func read() -> UInt {
>         return 1
>     }
>     func read<T>() -> T {
>         print("Unsupported data type requested")
>         exit(1)
>     }
> }
>
>
> Objects of that class return the requested type as expected when used like
> so:
>
> let thisWorks: Int = Bar().read() // returns -1
> let thisAlsoWorks: UInt = Bar().read() // returns 1
>
>
> However, when I introduce generics on top of that class, the expected
> method (the "most precise" method) is not called. For example, given this
> other class:
>
> class Baz<T> {
>     let myBar = Bar()
>
>     func read() -> T {
>         return self.myBar.read()
>     }
> }
>
>
> Both of these invocations call the generic read<T>() -> T method rather
> than the read() -> UInt method:
>
> let thisDoesntWork = Baz<UInt>().read()
> let thisDoesntWorkEither: UInt = Baz<UInt>().read()
>
>
> Am I using generics wrong here? Is there some other language feature I
> should be using to capture this data? Any pointers would be greatly
> appreciated.
>
> Thank you,
> Ryan
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