Equivalent du mot-clé dynamic (C#) en Visual Basic
Bonjour tout le monde,
Ne jamais écrire 3 messages d'affilés sans 4 sur un forum dit-on ... non :P ?
J'ai traduit le code suivant en VB : http://blogs.msdn.com/b/shawnhar/arc...c-dynamic.aspx
Code:
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Namespace SampleHeritage
Class Animal
End Class
Class Cat : Inherits Animal
End Class
Class Dog : Inherits Animal
End Class
Class Mouse : Inherits Animal
End Class
Module M1
'We can create several overloads of the same method, specialized according to different combinations of their parameter types:
Sub ReactSpecialization([me] As Animal, other As Animal)
Console.WriteLine("{0} is not interested in {1}.", [me], other)
End Sub
Sub ReactSpecialization([me] As Cat, other As Dog)
Console.WriteLine("Cat runs away from dog.")
End Sub
Sub ReactSpecialization([me] As Cat, other As Mouse)
Console.WriteLine("Cat chases mouse.")
End Sub
Sub ReactSpecialization([me] As Dog, other As Cat)
Console.WriteLine("Dog chases cat.")
End Sub
'And now the magic part:
Sub React([me] As Animal, other As Animal)
ReactSpecialization([me], other)
End Sub
'This works because of the "as dynamic" cast, which tells the C# compiler,
'rather than just calling ReactSpecialization(Animal, Animal),
'to dynamically examine the type of each parameter and make a runtime choice
'about which method overload to invoke.
'To prove it really works:
Sub Test()
Dim cat As Animal = New Cat()
Dim dog As Animal = New Dog()
Dim mouse As Animal = New Mouse()
React(cat, dog)
React(cat, mouse)
React(dog, cat)
React(dog, mouse)
End Sub
'Output:
' Cat runs away from dog.
' Cat chases mouse.
' Dog chases cat.
' Dog is not interested in Mouse.
End Module
End Namespace |
En langage C# et en utilisant un type Dynamic (as dynamic), la sortie du Debug.Print est:
Code:
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'Output:
' Cat runs away from dog.
' Cat chases mouse.
' Dog chases cat.
' Dog is not interested in Mouse. |
Si on essaye ce code en VB, la sortie sera:
Code:
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' Cat is not interested in Dog.
' Cat is not interested in Mouse.
' Dog is not interested in Cat.
' Dog is not interested in Mouse. |
parce que j'ai remplacé le Type dynamic (C#) en type Animal.
D'après vous, comment obtenir le même résultat qu'en C#.
On voit qu'en exécutant le code, le "Sous-type" est bien respectivement Cat, Dog et Mouse lors de l'initialisation dans la procédure Sub Test().
Merci.
@+
