Structural Patterns – Adapter

Adapter – Allows unrelated objects with an incompatible interface to collaborate.

From Design Patterns – Structural Patterns

Structure

Applicability

When the project has some existing class, the interface class isn’t compatible with the rest of the project code.

It is used when the developer wants to reuse a few existing sub-class that lack common functionally and can’t be added by the source code to the sub-classes.

Pros and Cons

How to Implement

The adapter patterns have two methods that can implement, such as the object adapter and the class adapter.

#1 Basic Sample

1. Object adapter

static void Main(string[] args)
{
    Adaptee adaptee = new Adaptee();
    ITargert targert = new Target(adaptee);

    Console.WriteLine(targert.GetReuqest());

    Console.ReadKey();
}

public interface ITargert
{
    string GetReuqest();
}

public class Adaptee
{
    public string GetSpecificRequest() => "Specific reuqest";
}

public class Target : ITargert
{
    private readonly Adaptee adaptee;

    public Target(Adaptee _daptee)
    {
 this.adaptee = _daptee;
    }

    public string GetReuqest() => $"This is '{this.adaptee.GetSpecificRequest()}'";
}

2. Class adapter

static void Main(string[] args)
{
    Adaptee adaptee = new Adaptee();
    ITargert targert = new Target();

    Console.WriteLine(targert.GetReuqest(adaptee));

    Console.ReadKey();
}

public interface ITargert
{
    string GetReuqest(Adaptee adaptee);
}

public class Adaptee
{
    public string GetSpecificRequest() => "Specific reuqest";
}

public class Target : ThirdPartyClass, ITargert
{
    public string GetReuqest(Adaptee adaptee) => $"This is '{GetThirdPartRequest(adaptee)}'";
}

public class ThirdPartyClass
{
    public string GetThirdPartRequest(Adaptee adaptee) => adaptee.GetSpecificRequest();
}

#2 Web Application Project

Step 1 Create the generic repository mechanism in the Core project and the Infra project. The interface class file name sets “IAdapter_Obj.” Another interface class file name sets “IAdapter_Class.” The repository class file name sets “AdapteRepo_Obj.” Another repository class file name sets “AdapteRepo_Class.”

Step 2 Create the new class files called “Adaptee_Obj” and “Adaptee_Class” under the Core project.

• Adaptee_Obj & Adaptee_Class are same as source code logic.

public class Adaptee_Class<T> where T : class
{
 public IEnumerable<T> CopyToObject(List<T> obj)
 {
  List<T> result = new List<T>();
  result.AddRange(obj);
  result.AddRange(obj);

  return result.ToList();
 }
}

Step 3 AdapterRepo_Obj source code and AdapterRepo_Class source code have a few part differences. The source code shows below:

• Object adapter – AdapterRepo_Obj

public class AdapterRepo_Obj<T> : IAdapter_Obj<T> where T : class
{
 private readonly Adaptee_Obj<T> adaptee;
 private readonly IGenericTypeRepository<T> repo;

 public AdapterRepo_Obj(IGenericTypeRepository<T> _repo)
 {
  this.adaptee = new Adaptee_Obj<T>();
  this.repo = _repo;
 }

 public IEnumerable<T> GetRequest()
 {
  try
  {
   List<T> obj = repo.GetAll().Result as List<T>;
 
   if (obj.Count != 0)
    return this.adaptee.CopyToObject(obj);
   else
    return new List<T>();
  }
  catch (Exception e)
  {
   return new List<T>();
  }
 }
}

• Class adapter – AdapterRepo_Class

public class AdapterRepo_Class<T> : Adaptee_Class<T> ,IAdapter_Class<T> where T : class
{
 private readonly IGenericTypeRepository<T> repo;

 public AdapterRepo_Class(IGenericTypeRepository<T> _repo)
 {    
     this.repo = _repo;
 }

 public IEnumerable<T> GetRequest(Adaptee_Class<T> adaptee_Class)
 {
     try
     {
  List<T> obj = repo.GetAll().Result as List<T>;

  if (obj.Count != 0)
      return CopyToObject(obj);
  else
      return new List<T>();
         }
         catch (Exception e)
            {
  return new List<T>();
     }
 }
}

Step 4 Create the new controller file and the view file under the web project. New controller file name sets “AdapterController.” The view part only creates the Index page.

Reference

• Refactoring.Guru – Adapter
• DOT NET TUTORIALS – Adapter Design Pattern in C#