1.2 KiB
1.2 KiB
title
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| Generics |
Generics
Write a name inside angle brackets to make a generic function or type.
func makeArray<Item>(repeating item: Item, numberOfTimes: Int) -> [Item] {
var result = [Item]()
for _ in 0..<numberOfTimes {
result.append(item)
}
return result
}
makeArray(repeating: "knock", numberOfTimes: 4)
You can make generic forms of functions and methods, as well as classes, enumerations, and structures.
// Reimplement the Swift standard library's optional type
enum OptionalValue<Wrapped> {
case none
case some(Wrapped)
}
var possibleInteger: OptionalValue<Int> = .none
possibleInteger = .some(100)
Use where right before the body to specify a list of requirements—for example, to require the type to implement a protocol, to require two types to be the same, or to require a class to have a particular superclass.
func anyCommonElements<T: Sequence, U: Sequence>(_ lhs: T, _ rhs: U) -> Bool
where T.Element: Equatable, T.Element == U.Element
{
for lhsItem in lhs {
for rhsItem in rhs {
if lhsItem == rhsItem {
return true
}
}
}
return false
}
anyCommonElements([1, 2, 3], [3])