Is this proper in OO theory?

[Daniel Billingsley]

The base class obviously can't know anything about a class which inherits
from it, but is it acceptable to have a base class method which will be
given information from an inherited class?

For (a stupid) example:

-----------

public abstract class BaseClass
{
private int _someInteger=0;

protected int AddNumbers(int anotherNumber)
{
return anotherNumber + _someInteger;
}

}

public class Class2 : BaseClass
{
private int _anotherInteger;
public int GetANumber()
{
return base.AddNumber(_anotherInteger);
}
}

----------

The underlying issue is that the generic code in the AddNumbers method from
example is known to be needed in all the classes inheriting from BaseClass,
but needs some additional information based on the specifics of the
inherited class (it's a data access method in reality).

 

[Marina]

I don't feel like I'm getting a clear example of the issue from this
particular code sample.

In general, there is nothing wrong with putting anything in the base class
that will be useful to all its children, even if it requires some
parameters.

 

[David Browne]

The base class obviously can't know anything about a class which inherits
from it, but is it acceptable to have a base class method which will be
given information from an inherited class?

For (a stupid) example:

-----------

public abstract class BaseClass
{
private int _someInteger=0;

protected int AddNumbers(int anotherNumber)
{
return anotherNumber + _someInteger;
}

}

public class Class2 : BaseClass
{
private int _anotherInteger;
public int GetANumber()
{
return base.AddNumber(_anotherInteger);
}
}

Sure that's fine. Although it's more usually implemented using an abstract
method in the base class like this:

public abstract class BaseClass
{
private int _someInteger=0;

protected int GetANumber()
{
return GetAnotherNumber() + _someInteger;
}
abstract int GetAnotherNumber();
}

public class Class2 : BaseClass
{
private int _anotherInteger;
public int GetAnotherNumber()
{
return _anotherInteger;
}
}

So each concrete BaseClass subtype must implemente GetAnotherNumber, which
allows methods implemented in BaseClass to invoke GetAnotherNumber even
though BaseClass does not implement that method.


David

 

[Daniel Billingsley]

You've changed the question a bit, but your answer is very useful
nonetheless. Thanks.