[R] Very simple question R5 setRefClass and Initialize

[Julien Cochennec]

Hi,
New to this list, and glad I found R5 which si a great improvement to R 
for my work.
Something seems odd anyway, when I do a setRefClass, the initialize 
method execute at the class definition.
I would like it to execute only when an instance is created.
How can I do that? I found no way to test if the code execution is when 
the class definition happens or when a $new instance is created.
Thanks for your help.
For example my class definition looks like this :

mongoDbUser = setRefClass("mongoDbUser",
     fields = list(
     auth = "logical",
     host = "character",
         username = "character",
     password = "character",
         db = "character",
     connector = "mongo"
     ),
   methods = list(
     initialize = function(auth,host,username,password,db,connector){
       print("initialization")
     }
   )
)

If I execute this code, it says "initialization", but it shouldn't, I 
created no instance, right??
I would like "initialization" to appear only when I do :
mongoDbUser$new(...)