Today, we’ll talk about concrete constrained extensions and Availability by Swift Version. Simply speaking, it helps extend concrete type with concrete constraint. In the change log of Swift, a simple definition is given as following.
extension Array where Element == Int { }
It extends Array with concrete type Int which means the extension will only works on Int. Let’s show a simple extension to get the sum of elements in the array.
extension Array where Element == Int {
func sum() -> Int {
return reduce(0, +)
}
}
[1, 2, 4, 8].sum() // 15
In Swift 3.0, we can only use a protocol as constraint to extend concrete type. We will not give an example but you can find many example on Internet.
Thanks for your time.
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