On Jul 26, 2015, at 16:30 , Michael de Haan <m...@comcast.net> wrote:
>
> func genericFor<T>(s:String) -> T {
>
> return T(s)! // error. ’T’ cannot be constructed because it has no
> accessible initializers
> }
This *generic* definition asks for an invocation of ‘init (_ s: String)’ *for
any type that satisfies the constraints on T*. Since there are no constraints,
this is only compilable if every type has a keywordless String-parameter
initializer, and that’s obviously not true.
If this were a template (like an Obj-C macro, sorta), then the compiler could
take the actual type of T and see what initializers are available. But Swift
generics don’t work that way.
To do literally what you’re asking for, you’d have to declare a new protocol P
that contains the form of ‘init’ you want to use, then use protocol extensions
to add conformance to P, then write your function like this:
func genericFor<T: P> …
But it’s not clear that this is what you’re aiming at — your example doesn’t
need any generic function at all. That’s why I was asking about a more
realistic example of the problem you’re trying to solve.
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