Adapter

UML class diagram

Participants
The classes and objects participating in this pattern are:
- Target (
ChemicalCompound
)- defines the domain-specific interface that Client uses.
- Adapter (
Compound
)- adapts the interface Adaptee to the Target interface.
- Adaptee (
ChemicalDatabank
)- defines an existing interface that needs adapting.
- Client (
AdapterApp
)- collaborates with objects conforming to the Target interface.
Structural code in C#
This structural code demonstrates the Adapter pattern which maps the interface of one class onto another so that they can work together. These incompatible classes may come from different libraries or frameworks.
using System;
namespace DoFactory.GangOfFour.Adapter.Structural
{
/// <summary>
/// MainApp startup class for Structural
/// Adapter Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Create adapter and place a request
Target target = new Adapter();
target.Request();
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Target' class
/// </summary>
class Target
{
public virtual void Request()
{
Console.WriteLine("Called Target Request()");
}
}
/// <summary>
/// The 'Adapter' class
/// </summary>
class Adapter : Target
{
private Adaptee _adaptee = new Adaptee();
public override void Request()
{
// Possibly do some other work
// and then call SpecificRequest
_adaptee.SpecificRequest();
}
}
/// <summary>
/// The 'Adaptee' class
/// </summary>
class Adaptee
{
public void SpecificRequest()
{
Console.WriteLine("Called SpecificRequest()");
}
}
}
Output
Real-world code in C#
This real-world code demonstrates the use of a legacy chemical databank. Chemical compound objects access the databank through an Adapter interface.
using System;
namespace DoFactory.GangOfFour.Adapter.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Adapter Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Non-adapted chemical compound
Compound unknown = new Compound("Unknown");
unknown.Display();
// Adapted chemical compounds
Compound water = new RichCompound("Water");
water.Display();
Compound benzene = new RichCompound("Benzene");
benzene.Display();
Compound ethanol = new RichCompound("Ethanol");
ethanol.Display();
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Target' class
/// </summary>
class Compound
{
protected string _chemical;
protected float _boilingPoint;
protected float _meltingPoint;
protected double _molecularWeight;
protected string _molecularFormula;
// Constructor
public Compound(string chemical)
{
this._chemical = chemical;
}
public virtual void Display()
{
Console.WriteLine("\nCompound: {0} ------ ", _chemical);
}
}
/// <summary>
/// The 'Adapter' class
/// </summary>
class RichCompound : Compound
{
private ChemicalDatabank _bank;
// Constructor
public RichCompound(string name)
: base(name)
{
}
public override void Display()
{
// The Adaptee
_bank = new ChemicalDatabank();
_boilingPoint = _bank.GetCriticalPoint(_chemical, "B");
_meltingPoint = _bank.GetCriticalPoint(_chemical, "M");
_molecularWeight = _bank.GetMolecularWeight(_chemical);
_molecularFormula = _bank.GetMolecularStructure(_chemical);
base.Display();
Console.WriteLine(" Formula: {0}", _molecularFormula);
Console.WriteLine(" Weight : {0}", _molecularWeight);
Console.WriteLine(" Melting Pt: {0}", _meltingPoint);
Console.WriteLine(" Boiling Pt: {0}", _boilingPoint);
}
}
/// <summary>
/// The 'Adaptee' class
/// </summary>
class ChemicalDatabank
{
// The databank 'legacy API'
public float GetCriticalPoint(string compound, string point)
{
// Melting Point
if (point == "M")
{
switch (compound.ToLower())
{
case "water": return 0.0f;
case "benzene": return 5.5f;
case "ethanol": return -114.1f;
default: return 0f;
}
}
// Boiling Point
else
{
switch (compound.ToLower())
{
case "water": return 100.0f;
case "benzene": return 80.1f;
case "ethanol": return 78.3f;
default: return 0f;
}
}
}
public string GetMolecularStructure(string compound)
{
switch (compound.ToLower())
{
case "water": return "H20";
case "benzene": return "C6H6";
case "ethanol": return "C2H5OH";
default: return "";
}
}
public double GetMolecularWeight(string compound)
{
switch (compound.ToLower())
{
case "water": return 18.015;
case "benzene": return 78.1134;
case "ethanol": return 46.0688;
default: return 0d;
}
}
}
}
Output
Compound: Water ------
Formula: H20
Weight : 18.015
Melting Pt: 0
Boiling Pt: 100
Compound: Benzene ------
Formula: C6H6
Weight : 78.1134
Melting Pt: 5.5
Boiling Pt: 80.1
Compound: Alcohol ------
Formula: C2H6O2
Weight : 46.0688
Melting Pt: -114.1
Boiling Pt: 78.3
.NET Optimized code in C#
The .NET optimized code demonstrates the
same real-world situation as above but uses modern, built-in .NET features,
such as, generics, reflection, LINQ, lambda functions, and more.
You can find an example on our Singleton pattern page.
All other patterns, and so much more, are available in our Dofactory .NET product.
Dofactory .NET includes the Gang of Four and Enterprise patterns, but also many other innovations including our Ultra-Clean™ Architecture, powerful low-code tactics, Rapid Application Development (RAD) techniques, and much more.
Accelerate your application development to where you can write entire solutions in just 33 days!. This unique package will change your outlook on development and your career. Here's what is included:
- 69 gang-of-four pattern projects
- 46 head-first pattern projects
- Fowler's enterprise patterns
- Multi-tier patterns
- Convention over configuration
- Active Record and CQRS patterns
- Repository and Unit-of-Work patterns
- MVC, MVP, & MVVM patterns
- SparkTM Rapid App Dev (RAD) data access
- Complete Analytics, Dashboard App
- Complete Art Shop, Ecommerce App
- Complete SaaS, Multi-Tenant App
- Complete CRM, Customer Relationship App
- 33-Day App Factory™
- Everything 100% source code