Should static variables be replaced with enums?

Question

So I was looking at some code that was checked in and I got all puzzled over:

// Amount of days before cancellation can't be done
enum Cancellation { Limit = 2 };

Asking the guy who checked it in he argued that it's much better to use enums instead of static variables, bettern than this:

private static int CANCELLATION_LIMIT = 2;

So we started arguing. My argument was that he was using enum as a way to store values (it'll break if there were two enum symbols with the same value). He argued it was an antipattern to have static variables in a class.

My question is what best practice should be used for either?

Answer 1

Enums are typed.

That is, if you have a method where you have to pass a certain 'state' to a method for instance, you can only pass 'valid' arguments. For instance:

enum OrderState 
{
  pending = 1,
  shipped = 2
}

public IList<Order> GetOrdersInState( OrderState )
{
}

This is a good example -imho- of using enums. When OrderState is an int for which you create 2 const ints, you have no restriction and are able to pass invalid values. The compiler won't complain.

However, the case that you're bringing up, I think using enums is not a valid solution. It's a misuse of using an int, and a const int should be used.

Enums are good, but they should be used where they must be used. They're not the preferred tool in every situation. Having a const or static var is in this case not an antipattern.

Answer 2

return "Is it logically a set of values" ? "Enum is appropriate" : "Static const is fine"

(I'm a big fan of the logically consistent)

Answer 3

No, How do you define static string variables or decimal values in enum?

Answer 4

I don't think that CANELLATION_LIMIT sounds like an enum, which is usually a set of choices.

For something different, if it was a const, then maybe... but currently it is a mutable field?

Note that enums are limited to integer-based types, so it can't be used for float, string, etc.

Answer 5

For immutable values intended to be unique, enumerations are the way to go. The question to ask is simple: should the object store the value itself, even statically? In many cases, such as when describing errors or action, the answer is no. Remember, enums was born as a replacement for #define: it associates typical values with identifiers and it provides a type, it doesn't actually say "store this constant here".

I presume you don't actually want to store anything, but provide such typical values. static const members are only useful when you intend to use them as such, for example if you need to pass them by reference to a method.

Answer 6

I think that you should use enums if you have a set of values directly connected.

Something like: enum Status { Open = 1, Closed =2, Waiting=3 };

For everything else, I'd say static variables are the way to go.

Answer 7

I don't know that it is an anti-pattern to have static variables in a class (?). For example, the Color class in the .Net framework has lots of static public variables, such as Color.Red. So, from that perspective, I would agree with you.

However, there may be a compromise: use private const CANCELLATION_LIMIT = 2; and both of your should be happy. For him, there will be no global variable for the class (?), as the consts will be replaced by the compiler, and you will get a single point of change with a clear name.