Re: Inheritance: Can the base class access a function in the class
which is inheriting from it?
ngoonee@gmail.com wrote:
On Mar 14, 1:23 pm, red floyd <no.s...@here.dude> wrote:
ngoo...@gmail.com wrote:
Hi all,
My intent is to code some algorith which repeatedly applies a certain
comparison function in C++. The algorithm itself works fine, but I'm
searching for easy ways to select the comparison function to be
applied, preferably at run-time (ie. no preprocessor defines).
A very simplified example of the idea I had:-
class baseclass {
private:
virtual int compare(int a,int b);
public:
int do_something(int a, int b) {
return compare(a,b);
}
};
class class2:public baseclass {
private:
int compare(int a,int b) {
return (b-a);
}
public:
};
class class1:public baseclass {
private:
int compare(int a,int b) {
return (a-b);
}
public:
};
Hence, if I create an instance of class1 and call the function
do_something, I'd like it to access the compare() function within
class1. Obviously, however, it doesn't work as is, meaning the method
I'm trying is not legal.
1. Could anyone suggest a legal way of doing what I'm trying to
accomplish, besides simply copy-pasting the whole code of
do_something() into a seperate class?
2. Is there any other way besides class inheritance to accomplish the
above?
What doesn't work?
The only problem that I can see is that you haven't implemented
baseclass::compare. Either provide an implmeentation or declare it as
pure virtual.
Perhaps I wasn't being clear enough, apologies. I don't want to (in
any situation) use baseclass::compare. I will not be creating any
objects of class baseclass, only of class1 and class2. I would like
class1 and class2 to be able to use baseclass's do_something()
function, but using their own unique versions of compare().
Then declare it pure virtual...
Note the "= 0" in the class below.
What you have created is a well known design pattern called "Template"
(not to be confused with C++ templates).
class baseclass {
private:
virtual int compare(int a,int b) = 0;
public:
int do_something(int a, int b) {
return compare(a,b);
}
};