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Consider something like this:
object Singleton
val cls: Class[Singleton] = ???
What do I have to write instead of ????
I tried classOf[Singleton], classOf[Singleton.type], Singleton.type, but nothing worked.
(I know of course about getClass, the runtime version of classOf, but that's not what I'm asking.)
980
We can distinguish a Singleton class from the usual classes with respect to the process of instantiating the object of the class. To instantiate a normal class, we use a java constructor. On the other hand, to instantiate a singleton class, we use the getInstance() method.
The most popular approach is to implement a Singleton by creating a regular class and making sure it has: A private constructor. A static field containing its only instance. A static factory method for obtaining the instance.
Unlike static classes, Singleton classes can be inherited, can have base class, can be serialized and can implement interfaces.
The Singleton is a useful Design Pattern for allowing only one instance of your class, but common mistakes can inadvertently allow more than one instance to be created.
Here a solution, but it's not pretty ...
object Singleton
val cls : Class[Singleton] = Singleton.getClass.asInstanceOf[Class[Singleton]]
Edit: completed the solution after reading another question/answer: Scala equivalent of Java java.lang.Class<T> Object
Note1: type erasure would prevent this from being particularly useful, e.g. in pattern matching. See referenced question/answer, above, for a good explanation
Note2: the scala -explaintypes flag is quite handy in understanding type errors.
HTH
60
You are not alone with this problem. The answer is: There is currently no way to avoid a Singleton.getClass. See this comment for more information why classOf[Singleton] does not work
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