Hiding an inherited method/property

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A Ratcliffe

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I have some classes that inherit from each other, as an example...

Point (abstract base class)

Point3 (for 3D points), derived from Point

Point4 (adds a homogenous co-ordinate) derived from Point3

Point3 has a Method - MoveBy(float dx, float dy, float dz), for moving it
relatively in 3D space.

Point4 has its own equivalent - MoveBy(float dx, float dy, float dz, float
dw), but I want to hide Point3's MoveBy, so it isn't available when you are
working with a Point4. There are other methods/properties of Point3 that
still make sense for Point4, so I don't want to love all the inherited
methods/properties.

Hope this makes sense, and thanks for all your help,

Yours,

Ann-Marie Ratcliffe
 
A Ratcliffe said:
I have some classes that inherit from each other, as an example...

Point (abstract base class)

Point3 (for 3D points), derived from Point

Point4 (adds a homogenous co-ordinate) derived from Point3

Point3 has a Method - MoveBy(float dx, float dy, float dz), for moving it
relatively in 3D space.

Point4 has its own equivalent - MoveBy(float dx, float dy, float dz, float
dw), but I want to hide Point3's MoveBy, so it isn't available when you are
working with a Point4. There are other methods/properties of Point3 that
still make sense for Point4, so I don't want to love all the inherited
methods/properties.
Click to expand...

It sounds like your Point4 shouldn't be derived from a Point3 - it
breaks Liskov's Substitutability Principle (namely that whatever you
can do with a Point3, you should be able to do with a Point4).
 
It sounds like your Point4 shouldn't be derived from a Point3 - it
breaks Liskov's Substitutability Principle (namely that whatever you
can do with a Point3, you should be able to do with a Point4).
Click to expand...

Looks like you are right on that basis. Actually, these are 'helper'
functions for the individual classes. Everything else works correctly, but
these are just meant to provide a quicker way of moving/setting the points
than individually setting the co-ords.

On that basis, they could be removed and I wouldn't have this problem. But
Helper functions/methods are developer-friendly...

Thanks for your help,

Ann-Marie
 
If it makes sense, you might make a MoveBy(dx, dy,dz) in Point 4 that
calls the 4 argument version with dw=0. That way Point4 is logically related
to Point3. [Perhaps that makes no sense in your case, but it's worth
considering]
Bob
 
Mon, 3 Nov 2003 12:46:13 -0000, on
microsoft.public.dotnet.languages.csharp, A Ratcliffe wrote:

[...]
Point3 has a Method - MoveBy(float dx, float dy, float dz), for moving it
relatively in 3D space.

Point4 has its own equivalent - MoveBy(float dx, float dy, float dz, float
dw), but I want to hide Point3's MoveBy, so it isn't available when you are
working with a Point4. There are other methods/properties of Point3 that
still make sense for Point4, so I don't want to love all the inherited
methods/properties.
Click to expand...
[...]

Hi
If I've understood correctly, the "new" keyword should be the cure for your
problem :)
In Point4 you should define method MoveBy starting with "new" keyword.
Have you tried this?

Greetz
Piotr Olech
 
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