On 31 mar, 11:05, <[EMAIL PROTECTED]> wrote:
> Hello everyone
>
> I have defined some sort of 'interface class' and a factory function that
> creates instance objects of specific classes, which implement that interface:
>
> Interface definition:
> ***************************************************************************************
> import GUI.webGUI as webGUI
>
> class EditInterface(webGUI.WebGUI):
> def addEntry(self, *p):
> raise 'EditInterface.addEntry(): Interface must not be called
> directly'
You want:
raise NotImplementedError('EditInterface.addEntry():
Interface must not be called directly')
And unless you have some pretty good reason to do so (ie: template
methods in EditInterface depending on these methods), you don't even
want to bother with all this - just document which methods must be
implemented, and let Python raise an AttributeError if they are not.
(snip)
> Factory:
> ***************************************************************************************
> def factory(type, *p):
> if type == common.databaseEntryTypes[0]:
> return module1.Class1(*p);
> elif type == common.databaseEntryTypes[1]:
> return module2.Class2(*p);
> elif type == common.databaseEntryTypes[2]:
> return module3.Class3(*p);
> elif type == common.databaseEntryTypes[3]:
> return module4.Class4(*p);
The whole point of polymorphic dispatch in OO is to avoid this kind of
mess. What's wrong with instanciating classes directly ? NB : in
Python, classes are objects too, so you can pass them around as
needed. Also, instanciation is done thu a call to the class object -
which makes it just the same as a function call. IOW, you just don't
need a clumsy dedicated factory function just to make sure the client
code is not too tightly coupled to the exact implementation.
>
> Implementing Class1:
> ***************************************************************************************
> import editInterface
>
> class Class1(editInterface.EditInterface):
>
> def __init__(self, product, database):
> # do something here ...
>
> def showEntry(self, entry, statustext):
> # do something here as well, return some string...
> ***************************************************************************************
>
> Now, when I want to create an Instance of Class1 I do:
>
> myClass1Instance = factory.factory(common.databaseEntryTypes[1], 'Name',
> databaseObj )
> Which seems to work fine according to the debugger. But when I do next:
>
> msg = myClass1Instance.show(firstEntry, '')
>
> Then the show() method of the class 'EditInterface' is called instead of the
> show() method of the class 'Class1' !!
Reread your code : class Class1 have no 'show' method !-)
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