枚举中的业务逻辑？

Question

Is it considered good practice to put any type of business logic in Enums? Not really intense logic, but more of like convenience utility methods. For example:

public enum OrderStatus {

 OPEN, OPEN_WITH_RESTRICTIONS, OPEN_TEMPORARY, CLOSED;


 public static boolean isOpenStatus(OrderStatus sts) {
      return sts == OPEN || sts == OPEN_WITH_RESTRICTIONS || sts == OPEN_TEMPORARY;
 }

}

Answer 1

IMHO, this enables you to put relevant information right where it's likely to be used and searched for. There's no reason for enums not to be actual classes with actual responsibility.

If this allows you to write simpler code, and SOLID code, why not?

Answer 2

Yes, i think this is a good idea. However, i think it can be implemented much more cleanly using instance methods:

public enum OrderStatus {

 OPEN, OPEN_WITH_RESTRICTIONS, OPEN_TEMPORARY, 
 CLOSED {
   @Override isOpen() { return false; }
 };

 public boolean isOpen()
 { 
   return true;
 }
}

Answer 3

I often use Enums for singleton instances. Thus they contain almost only business logic. Being classes that implcitly extend Enum they can even implement interfaces.

I'd only consider using Enums if it fits to the enumerated values, ie the buisness logic is tightly coupled with the instances.

Answer 4

由于您示例中的逻辑与枚举值的（名称）紧密相关，我想不出更好的地方来放置它。

Answer 5

Enums primary job is the enforce a specific set of values with programmer friendly names. If you business logic can be expressed as a static set of values then Enums are a good way to go. Don't forget that in Java you can create Enum classes which hold more than one value , useful if you have a bunch of related values.

Answer 6

For simple buisness logic as above it is ok, but i ran into a problem when it comes to the point of extending enums which is not possible. For example we stored additional data within the enums and later wanted to get a reverse mapping of the values for many different enums which would be easy with standard classes but is impossible with enums (without code duplication).
Standard classes can do the same (except of using in switch statements) and are more flexible and reliable. If the enumeration may get more complicated logic better use classes otherwise using enum with simple logic is quite fine in my opinion