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3 min readFeb 6, 2026
Swift

How to Add Default Protocol Implementations

Provide shared behavior with protocol extensions.

Steps

  1. Paste the code into a Swift file or playground.
  2. Run it once to verify the output.
  3. Adjust the inputs to match your use case.

Copy and paste

import Foundation

protocol Loggable {
    func log(message: String)
}

extension Loggable {
    func log(message: String) {
        print("LOG:", message)
    }
}

struct Service: Loggable {}

let service = Service()
service.log(message: "Ready")

Notes

  • Keep functions small and focused for reuse.
  • Prefer safe APIs like optionals and guards.