var ivar = [:]
ivar.className // __NSDictionaryI
var i = 1
i.className // error: ‘Int‘ does not have a member named ‘className‘
If you want to get the type of a primitive, you have to use bridgeToObjectiveC().
Example:
var i = 1
i.bridgeToObjectiveC().className // __NSCFNumber
println("\(object_getClassName(now))");