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// Adapter Pattern - Simple Judith Bishop Oct 2007 // Simplest adapter using interfaces and inheritance Existing way requests are implemented class Adaptee { // Provide full precision public double SpecificRequest(double a, double b) { return a / b; } }

// Required standard for requests interface ITarget { // Rough estimate required string Request(int i); }

// Implementing the required standard via Adaptee class Adapter : Adaptee, ITarget { public string Request(int i) { return "Rough estimate is " + (int)Math.Round(SpecificRequest(i, 3)); } }

class Client { static void Main() { // Showing the Adapteee in standalone mode Adaptee first = new Adaptee(); Console.Write("Before the new standard\nPrecise reading: "); Console.WriteLine(first.SpecificRequest(5, 3)); // What the client really wants ITarget second = new Adapter(); Console.WriteLine("\nMoving to the new standard"); Console.WriteLine(second.Request(5)); } }

/* Output 42 Before the new standard 43 Precise reading: 1.66666666666667 44 45 Moving to the new standard 46 Rough estimate is 2 47 */

// ITarget interface public interface IAircraft { bool Airborne { get; } void TakeOff(); int Height { get; } }

// Target public sealed class Aircraft : IAircraft { int height; bool airborne; public Aircraft() { height = 0; airborne = false; } public void TakeOff() { Console.WriteLine("Aircraft engine takeoff"); airborne = true; height = 200; // Meters } public bool Airborne { get { return airborne; } } public int Height { get { return height; } } }

// Adaptee interface public interface ISeacraft { int Speed { get; } void IncreaseRevs(); }

// Adaptee implementation public class Seacraft : ISeacraft { int speed = 0; public virtual void IncreaseRevs() { speed += 10; Console.WriteLine("Seacraft engine increases revs to " + speed + " knots"); } public int Speed { get { return speed; } } }

// Adapter public class Seabird : Seacraft, IAircraft { int height = 0; // A two-way adapter hides and routes the Target's methods // Use Seacraft instructions to implement this one public void TakeOff() { while (!Airborne) IncreaseRevs(); } // Routes this straight back to the Aircraft public int Height { get { return height; } } // This method is common to both Target and Adaptee public override void IncreaseRevs() { base.IncreaseRevs(); if (Speed > 40) height += 100; } public bool Airborne { get { return height > 50; } } }

static void Main() { // No adapter Console.WriteLine("Experiment 1: test the aircraft engine"); IAircraft aircraft = new Aircraft(); aircraft.TakeOff(); if (aircraft.Airborne) Console.WriteLine( "The aircraft engine is fine, flying at " + aircraft.Height + "meters"); // Classic usage of an adapter Console.WriteLine("\nExperiment 2: Use the engine in the Seabird"); IAircraft seabird = new Seabird(); seabird.TakeOff(); // And automatically increases speed Console.WriteLine("The Seabird took off"); // Two-way adapter: using seacraft instructions on an IAircraft object // (where they are not in the IAircraft interface) Console.WriteLine("\nExperiment 3: Increase the speed of the Seabird:"); ((ISeacraft)seabird).IncreaseRevs(); (seabird as ISeacraft).IncreaseRevs(); if (seabird.Airborne) Console.WriteLine("Seabird flying at height " + seabird.Height + " meters and speed " + (seabird as ISeacraft).Speed + " knots"); Console.WriteLine("Experiments successful; the Seabird flies!"); }

/* Output Experiment 1: test the aircraft engine Aircraft engine takeoff The aircraft engine is fine, flying at 200 meters Experiment 2: Use the engine in the Seabird Seacraft engine increases revs to 10 knots Seacraft engine increases revs to 20 knots Seacraft engine increases revs to 30 knots Seacraft engine increases revs to 40 knots Seacraft engine increases revs to 50 knots The Seabird took off Experiment 3: Increase the speed of the Seabird: Seacraft engine increases revs to 60 knots Seacraft engine increases revs to 70 knots Seabird flying at height 300 meters and speed 70 knots Experiments successful; the Seabird flies!