Can you create a singleton in Julia?

Question

I know that Julia does not have OOP but that multiple dispatch enables similar ideas. Given how seemingly contentious the use of singletons are in Python, I am wondering if there is a similar idea Julia (i.e. a struct that can only be instantiated once).

I am wondering if there's a way to have the constructor keep track of the number of times an object was instantiated with a global var or something like that? Or it's altogether not be possible?

Answer 1

The main way people make singletons in Julia is to define an empty struct (which means that it has 0 size), and define methods that return information for it.

struct Singleton
end
data(::Singleton) = "whatever you want it to do"

etc.