From: Marek Janukowicz Date: 2003-05-24T08:48:13+09:00 Subject: Strange Observable behavour I use Observable module in one of my projects. I noticed something strange and don't know if it is intentional. The add_observer method adds (surprise!) an observer for an object, but it does not check if this observer is not already registered for this object. Thus it is possible to add the same observer multiple times for the same Observable object. In my library I do some deletion in "update" method - if the observer is registered twice, the deletion is done twice, which is undesirable. There is no method to add observer conditionally, that is, to check if it is already added! Is there any way to add an observer if and only if it wasn't already registered for a particular Observable object? -- Marek Janukowicz