I am using Swift 4 and looking for a way to create extension function for array collection with arguments of type
typealias Listener<T> = (T) -> Void
however extension below cannot be created (Use of undeclared type 'T')
extension Sequence where Element == Listener<T>{
func callAll(t: T){
self.forEach { $0(t) }
}
}
Is there a way to make it work?
You cannot introduce new generic parameters at the header of an extension like T in your code, but each method can have generic parameters.
typealias Listener<T> = (T) -> Void
extension Sequence {
func callAll<T>(t: T)
where Element == Listener<T>
{
self.forEach { $0(t) }
}
}
let listeners: [Listener<Int>] = [
{ print($0) },
{ print($0 * 2) },
]
listeners.callAll(t: 2)
