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# Observable Mixin
#
# Observers must respond to update
module Observable
def add_observer(observer)
@observer_peers = [] unless @observer_peers
unless defined? observer.update
raise NameError, "observer needs to respond to `update'"
end
@observer_peers.push observer
end
def delete_observer(observer)
@observer_peers.delete observer if @observer_peers
end
def delete_observers
@observer_peers.clear if @observer_peers
end
def count_observers
if @observer_peers
@observer_peers.size
else
0
end
end
def changed(state=TRUE)
@observer_state = state
end
def changed?
@observer_state
end
def notify_observers(*arg)
if @observer_peers and @observer_state
for i in @observer_peers
i.update(*arg)
end
@observer_state = FALSE
end
end
end
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