Lotushints

Another quite useful pattern is Adapter pattern. Adapters represent an interface between two different classes. For example imagine being a continental EU citizen travelling to UK. For you to plug in to UK power plug, you need an adapter that will take the interface your connector has and output the interface UK power plug demands.
Definition of Adapter pattern is:

The Adapter pattern converts the interface of a class into an interface the client expects. Adapter lets classes work together even if they couldn’t otherwise due to incompatible interfaces.

So how does this work in practice?

You will mostly need adapters when you will obtain code from someone else. But just for the sake of simplicity, we will look into unlikely scenario, when you will get a code that prints “Hello World!” and write an adaptor that displays “Hello adapters!” in message box using the same interface.

First you need a client class and it’s interface. As we know, interfaces are not implemented in LotusScript. Thus, an abstract class will be used instead. Then we’ll need a client class. Both are pasted below:

Class CHelloWorldInterface
	Sub printText ()
	End Sub
End Class

Class CHelloWorld As CHelloWorldInterface
	Sub printText ()
		Print "Hello World!"
	End Sub
End Class

Now, we need to create our interface that displays “Hello adapters!” in message box.

Class CHelloAdaptersInterface
	Sub msgboxText ()
	End Sub
End Class

Class CHelloAdapters As CHelloAdaptersInterface
	Sub msgboxText ()
		Messagebox "Hello Adapters!"
	End Sub
End Class

All we need now is an adapter.

Class CHelloAdpatersAdapter As CHelloWorldInterface
	m_helloAdapter As CHelloAdaptersInterface

	Sub new (helloAdapter As CHelloAdaptersInterface)
		Set Me.m_helloAdapter = helloAdapter
	End Sub

	Sub printText()
		Call m_helloAdapter.msgboxText()
	End Sub
End Class

And to bind it together, here is an agent that will output both results.

Sub Initialize
	Dim hw As CHelloWorld
	Dim ha As CHelloAdapters
	Dim haa As CHelloWorldInterface

	Set hw = New CHelloWorld ()
	Set ha = New CHelloAdapters ()
	Set haa = New CHelloAdaptersAdapter (ha)

	'test HelloAdapters
	Call ha.msgboxText()

	'test HelloWorld
	Call testHello (hw)

	'test HelloAdaptersAdapter
	Call testHello (haa)
End Sub

Sub testHello (hello As CHelloWorldInterface)
	Call hello.printText()
End Sub