Posted on 01 May 2020 . 1 min read
A protocol can defines a set of methods that can be adopted by any class, but we can’t write code inside. On the other hand, extensions gives us the power to write code inside methods, but it can only used for one type.
In Protocol Extensions, we can extend protocols to provide implementations to all conforming types rather than extending a particular type.
For example, we have an array named oddNumbers contains odd numbers and a set named evenNumbers that contains even numbers.
let oddNumbers: [Int] = [1,5,23,91]
let evenNumbers: Set = [34,56,12,78,22] Now, we have protocol Collection that can be extended to provide countItems() method which returns total numbers of items.
extension Collection {
func countItems() -> Int {
return count
}
}Both conforming types gain countItems method by extending the protocol and prints total number of items available.
print(oddNumbers.countItems())
print(evenNumbers.countItems())Protocol Extensions can’t extend or inherit from another protocol.
Don’t hesitate to contact me if you have any questions or queries. Follow me on twitter @gurjitpt for any updates.
Thanks!
Share this article
Written By
Gurjit Singh
I’m Computer Science graduate and an iOS Engineer who writes about Swift and iOS development. Follow me for more updates:
Discover articles by topics
SwiftUI Class Struct Networking XCode NSCache Enum Optionals Property Observers Closures Guard Reviews StoreKit App Store Algorithms Testing Operators Protocol Extensions Weak Unowned SwiftData WWDC23 GCD API Admob SwiftLint Lottie Foreach Objective-C UIKit NavigationSplitView