I am trying to do this:
protocol Fly {
}
class Bird: Fly {
}
func fetch<T: Fly>(model: T) {
print("Done")
}
let bird: Fly = Bird()
fetch(model: bird)
However I get this error:
Cannot invoke 'fetch' with an argument list of type '(model: Fly)'
I set let bird: Fly = Bird() to be of type Fly, shouldn't it work since the function fetch takes any object that conforms to that protocol?
Any thoughts?
You are creating with Fly object with Bird instance
Replace code
protocol Fly {
}
class Bird: Fly {
}
func fetch<T: Fly>(model: T) {
print("Done")
}
let bird: Bird = Bird() // Here is a problem
fetch(model: bird)
let bird: Fly = Bird() and pass that into the function if the function accepts any instance that conforms to Fly?
Fly Protocol doesn't confirm Fly it self . Bird doesfetch accept any type of type Fly? Or that doesn't make sense - not sure?Fly as argument.
let bird: Fly = Bird() is perfectly fine. I don't think that is the issue here.I set
let bird: Fly = Bird()to be of typeFly, shouldn't it work since the function fetch takes any object that conforms to that protocol?
The overload resolution of the fetch(model: bird) call is done statically at compile time. The bird instance has been explicitly annotated to be of type Fly (which happens to be a protocol which can hold, dynamically, instances conforming to it). Since protocols doesn't conform to themselves, a call to fetch(model: bird) will not be eligable to use the constrained generic method func fetch<T: Fly>(model: T), since the type of bird, namely Fly, does not fulfill the type constraint T: Fly.
func fetch<T>(model: T) where T: Fly. What you have typed is for subclassing I believe. But still it shows same error.func fetch(model: Fly)That will work fine,