Your feedback is appreciated. It was a long time I touched OO, and
perhaps I need to brush up my OO knowledge :)
/H.
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| -----Original Message-----
| From: Dave Carabetta [mailto:[EMAIL PROTECTED]
| Sent: Monday, January 19, 2004 16:26
| To: CF-Talk
| Subject: RE: Cfc inheritance and best practices
|
| >Hi,
| >
| >I'm a fairly new to CFCs (which seems cool). I have a little issue:
| >
| >I have two CFCs, let's call them CFCmain and CFCdao. CFCmain extends
| >CFCdao, the former supplies the main interfaces, while the latter
| >provides the data access (SQL) functions.
| >
| >I designed these to be unaware of any shared scopes. I set
| the dsn to
| >use using a property on CFCmain (it sets a default value when first
| >instatiated).
| >
| >But, the property value on CFCmain (THIS.dsn), is not
| accessible at all
| >to CFCdao -- right? And there is no way to have this property on
| >CFCdao, and it is then inherited to CFCmain (since you are
| not allowed
| >to use the this scope on a "base" object, right?).
| >
| >This means, in practice -- that the dsn string needs to be passed to
| >any of my CFCdao functions (where the dsn is needed).
| >
| >Please let me know if my logic is correct, and if there is any
| >preferred/alternative way to design this!
| >
|
| Well, in my mind, you're not using inheritance correctly. The
| "rule" I strictly go by for using inheritance is that you
| should be able to use the two objects in the following sentence:
|
| [child class] is a [parent class]
| car is a vehicle
|
| In your case CFCmain is *not* a CFCdao. You should be using
| the notion of "composition," which is to say that CFCmain
| *has* a CFCdao. To use composition in your case, I'd probably
| just make a createObject() call either in the
| quasi-constructor area or in my init() function (of which all
| of my CFCs have) of the CFCmain class and pass in the name of
| the dsn to the CFCdao's init() function.
|
| All that being said, you are correct that the parent class
| does not have access to THIS.dsn in the child class. The
| child class has access to the paren't variables, but not the
| reverse (that I'm aware of).
|
| Regards,
| Dave.
|
|
|
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