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Interfaces

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An interface is a specification for a set of public instance methods. An interface defines and enforces similarities between unrelated classes without having to derive one class from the other. All interfaces are public, even if you don't explicitly add the public keyword in front of the interface keyword in the classDeclaration code. The methods on an interface are also public.

To create an interface, follow these steps:

1. In Solution Explorer, right-click the project, and then select Add.
2. In the New Item dialog box, select Interface and then enter a name for the interface.
3. Select Add.

When you add the implements keyword on a class declaration, the class must declare the methods that are specified by the interface. A class declaration can implement multiple interfaces. List the interfaces after the single occurrence of the implements keyword and separate the interface names by using commas. All interface methods that a class implements must be explicitly declared as public by using the public keyword in the class. A class that implements an interface must also be declared as public. An interface can extend another interface by using the extends keyword. However, an interface can't extend more than one interface.

Interface example

In the following example, an Automobile class implements an IDrivable interface. The is keyword is supported and lets you test whether a class implements an interface.

public interface IDrivable
{
    public int getSpeed()
     {
     }

    public void setSpeed(int newSpeed)
     {
     }
}

class Automobile implements IDrivable
 {
   int m_speed;

   public int getSpeed()
    {
         return m_speed;
    }

   public void setSpeed(int newSpeed)
    {
         m_speed = newSpeed;
    }
 }

class UseAnAutomobile
 {
   void DriveAutomobile()
    {
       IDrivable yourIDrivable;
       Automobile myAutomobile;
       str sTemp = "object is not an IDrivable";
	
       myAutomobile = new Automobile();

       if (myAutomobile is IDrivable)
       {
          yourIDrivable = myAutomobile;
          yourIDrivable.setSpeed(42);
          sTemp = int2str(yourIDrivable.getSpeed());
       }

       Global::info(sTemp);
       return;
    }
}

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