Is it acceptable to inherit from a class just for clarity?

Question

Suppose I have a template/generic class that just store key/value pairs:

public class GenericDatabase<Key, T>
{
 public Dictionary<Key, T> Data { get; set; }               

 public GenericDatabase()
 {
   Data = new Dictionary<Key, T>();
 }
 ...
}

Is it acceptable to derive a class from it without introducing any new methods or member variables, just for clarity? For instance, say I want to have a character database:

public class CharacterDatabase : GenericDatabase<string, CharacterStat>
{
   // no new methods or member variables
}

score 3 · Accepted Answer · answered Feb 04 '13 at 06:29

3

IMO Introducing a level of inheritance for the sake of clarity would confuse other developers. I think Generic declaration is clear enough.

GenericDatabase<string, CharacterStat>

answered Feb 04 '13 at 06:29

Habib

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I would like to understand better; why would it be confusing? – Extrakun Feb 04 '13 at 08:53
@Extrakun, Suppose I am going to use your class in my code, then just by typing the class name `CharacterDatabase`, I won't be able to see if it is inherited from a generic class, Since you have the generic class in your code, I suppose you would use it for multiple types. Leaving it as a Generic class will let the developer know that there are other possible types which could interact with your class `GenericDatabase`. – Habib Feb 04 '13 at 09:10

score 1 · Answer 2 · edited May 23 '17 at 12:18

1

Its a different language.. but take a look at how c++ defines its std::string class.

typedef basic_string<char> string;

Just wanted to point out that this practise is not just common, but used by standard library writers themselves.

I would support such a step if you are going to use CharacterDatabase a significant number of times. Additionally I am not sure if C# provides any other simpler mechanism than inheritance for this (like C++'s typedef) but that would be prefered.

The using directive can be used like a typedef, but it affects only the file it is declared in.

using CharacterDatabase = GenericDatabase<string, CharacterStat>

edited May 23 '17 at 12:18

Community

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1

answered Feb 04 '13 at 06:30

Karthik T

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@Antonijn I would assume such things would transcend language borders.. Is there a reason this is frowned upon in the C# world? – Karthik T Feb 04 '13 at 06:34
typedefs are uncommon in C# and are generally avoided. – antonijn Feb 04 '13 at 15:18

score 1 · Answer 3 · answered Feb 04 '13 at 06:30

1

In OOP nothing would prevent you from doing that. However, I've seen in many places that they use Marker Interfaces rather than a base class to indicate something. Marker interfaces usually has no public member and would only be used to mark a class as an example of something.

You can take a look at these links:

Wikipedia => marker interface pattern

What is a marker interface

answered Feb 04 '13 at 06:30

Saeed Neamati

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I haven't worked with Java, thus I really don't know. But as the name suggests, `Cloneable` means that you should be able to call `instance.Clone()` method. Thus it shouldn't be actually a marker interface. – Saeed Neamati Feb 04 '13 at 06:35
What you suggest is what most developers would (justifiably) think. However, it is a marker interface with no methods. – cdmckay Feb 04 '13 at 06:39
Which is much lamented. Introducing a Cloneable interface which doesn't actually have a Clone() method was a huge mistake. (Although, even if it did have a Clone() method, it'd still be messed up because there's no way to differentiate between deep and shallow cloning.) – Matthew Watson Feb 04 '13 at 08:52

score 1 · Answer 4 · answered Feb 04 '13 at 20:11

For me it depends of concrete types used.

If I had

GenericDatabase<string, CharacterStat>

I would leave it as it is - it is clear. But if I had

GenericDatabase<string, ArrayList<Pair<CharacterStat,Integer> > >

then I would definitely give it a name, and a really explanatory one ;).

Is it acceptable to inherit from a class just for clarity?

4 Answers4