适配器设计模式
例如: 如果你购买 Iphone 8(或任何其他 Apple 产品),你需要很多适配器。因为默认接口不支持音频 jac 或 USB。使用这些适配器,你可以使用带有电线的耳机,也可以使用普通的以太网电缆。因此 两个互不兼容的接口相互通信 。
因此,在技术术语中,这意味着: 将类的接口转换为客户期望的另一个接口。适配器让类一起工作,否则由于不兼容的接口。参与此模式的类和对象是:
适配器模式退出 4 个元素
- ITarget: 这是客户端用来实现功能的接口。
- Adaptee: 这是客户所需的功能,但其界面与客户端不兼容。
- 客户端: 这是希望通过使用适配器代码实现某些功能的类。
- 适配器: 这是实现 ITarget 并将调用客户端想要调用的 Adaptee 代码的类。
UML
https://i.stack.imgur.com/oYMFy.gif
第一个代码示例(理论示例) 。
public interface ITarget
{
void MethodA();
}
public class Adaptee
{
public void MethodB()
{
Console.WriteLine("MethodB() is called");
}
}
public class Client
{
private ITarget target;
public Client(ITarget target)
{
this.target = target;
}
public void MakeRequest()
{
target.MethodA();
}
}
public class Adapter : Adaptee, ITarget
{
public void MethodA()
{
MethodB();
}
}
第二个代码示例(真实世界的实现)
/// <summary>
/// Interface: This is the interface which is used by the client to achieve functionality.
/// </summary>
public interface ITarget
{
List<string> GetEmployeeList();
}
/// <summary>
/// Adaptee: This is the functionality which the client desires but its interface is not compatible with the client.
/// </summary>
public class CompanyEmplyees
{
public string[][] GetEmployees()
{
string[][] employees = new string[4][];
employees[0] = new string[] { "100", "Deepak", "Team Leader" };
employees[1] = new string[] { "101", "Rohit", "Developer" };
employees[2] = new string[] { "102", "Gautam", "Developer" };
employees[3] = new string[] { "103", "Dev", "Tester" };
return employees;
}
}
/// <summary>
/// Client: This is the class which wants to achieve some functionality by using the adaptee’s code (list of employees).
/// </summary>
public class ThirdPartyBillingSystem
{
/*
* This class is from a thirt party and you do'n have any control over it.
* But it requires a Emplyee list to do its work
*/
private ITarget employeeSource;
public ThirdPartyBillingSystem(ITarget employeeSource)
{
this.employeeSource = employeeSource;
}
public void ShowEmployeeList()
{
// call the clietn list in the interface
List<string> employee = employeeSource.GetEmployeeList();
Console.WriteLine("######### Employee List ##########");
foreach (var item in employee)
{
Console.Write(item);
}
}
}
/// <summary>
/// Adapter: This is the class which would implement ITarget and would call the Adaptee code which the client wants to call.
/// </summary>
public class EmployeeAdapter : CompanyEmplyees, ITarget
{
public List<string> GetEmployeeList()
{
List<string> employeeList = new List<string>();
string[][] employees = GetEmployees();
foreach (string[] employee in employees)
{
employeeList.Add(employee[0]);
employeeList.Add(",");
employeeList.Add(employee[1]);
employeeList.Add(",");
employeeList.Add(employee[2]);
employeeList.Add("\n");
}
return employeeList;
}
}
///
/// Demo
///
class Programs
{
static void Main(string[] args)
{
ITarget Itarget = new EmployeeAdapter();
ThirdPartyBillingSystem client = new ThirdPartyBillingSystem(Itarget);
client.ShowEmployeeList();
Console.ReadKey();
}
}
什么时候用
- 允许系统使用与其不兼容的其他系统的类。
- 允许新系统和现有系统之间的通信彼此独立
- Ado.Net SqlAdapter,OracleAdapter,MySqlAdapter 是 Adapter Pattern 的最佳示例。