Home » Extra libraries, Code snippets, applications etc. » C++ language problems and code snippets » Basic library interface and separation problem
| Basic library interface and separation problem [message #21860] |
Mon, 08 June 2009 15:51  |
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Most of my projects aren't very well designed, when I even bother to separate different functionality into different libraries, I often use internal knowledge of the underlying library, even without thinking about it.
For my most recent project, I wanted to have proper separation and I ran into the following issue:
LibA
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LibB
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App
suppose we have library 'LibA' and 'LibB', LibB uses LibA and exposes part of LibA's functionality to an application using LibB.
LibA contains class A,
class A {
enum a_attrs { foo, bar, foobar }
static void setAttr(a_attris an_attr);
}
LibB contains class B,
class B {
static void setAttr(a_attris an_attr)
{
A::setAttr(an_attr);
}
}
This is a very bad solution for me, because I want to be able to replace LibA with LibA2 later, _and_ I don't want the App to even be aware of the existence of LibA.
Also, as it is now the App will include the headers of class A, indirectly, because App will include the header of class B.
So now, App has a source code level dependency on LibA .
One way to solve this would be to give class B it's own enum
class B {
enum b_attrs { b_foo, b_bar, b_foobar }
static void setAttr(b_attrs an_attr);
}
void B::setAttr(b_attrs an_attr)
{
switch(an_attr)
{
case b_foo:
A::setAttr(foo);
break;
case b_bar:
A::setAttr(bar);
break;
case b_foobar:
A::setAttr(foobar);
break;
default:
break;
}
}
But when I add an attribute to class A, in would also have to edit class B to add the attribute there as well.
Any thought on how to solve this neatly ?
Greetings,
Jan
Jan (skyhawk)
[Updated on: Mon, 08 June 2009 15:52] Report message to a moderator |
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| Re: Basic library interface and separation problem [message #21877 is a reply to message #21876] |
Tue, 09 June 2009 08:22  |
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Koldo, sorry for the confusion, what I was looking was that:
When two classes need to share more then just basetypes, in my opinion you have two options:
- make one class depend on the other
- create a third class that serves as 'common' API for both.
I my case, because the two class are in separate libraries and I do not want source code dependencies between them; I've done what Didier and you suggested, created a third library that is shared/depended on by the other two which contains a class that serves as common API for both libraries.
Anyway, thanks for your swift responses!
Jan
Jan (skyhawk)
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