[Tutor] apply() after class?
Alan Gauld
alan.gauld at btinternet.com
Tue Feb 10 01:40:33 CET 2009
"Wayne Watson" <sierra_mtnview at sbcglobal.net> wrote
> Ah, another function without a link to a use. body, as in :
>
> class SetDecoderDialog(tkSimpleDialog.Dialog):
> def body(self,master):
> self.title("Set Video Decoder Register")
>
> Label(master, text='Register:').grid(row=0, sticky=W)
> Label(master, text='New Value:').grid(row=1, sticky=W)
>
> self.reg = Entry(master, width=10)
> self.val = Entry(master, width=10)
>
> self.reg.grid(row=0, column=1, sticky=W)
> self.val.grid(row=1, column=1, sticky=W)
>
> return self.reg
>
> def apply(self):
> reg = eval(self.reg.get())
> val = eval(self.val.get())
> self.gui.SetDecoder( reg, val )
>
> That's the end of the class. Is there something going on
> here between body-apply and tkSimpleDialog?
> Making them available to it?
Yes. This is part of the power of OOP.
If we create an instance of this class it inherits all of the
methods of simpleDialog. But if one of those methods internally
calls self.body or self.apply it will for this instance execute
SetDecoderDialog.body or SetDecoderDialog.apply
This is a form of polymorphism which is commonly used
in object frameworks.
Now I don't know whether SimpleDialog does do that
but it is entirely possible. Thus it would not seem like
anything is calling those two functions but in fact they
are being called indirectly. (A couple of print statements
would show whether they were or not!)
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld
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