Implementation of a map in which only weakly referenced keys are kept to the map values. This allows the garbage collector to reclaim these objects if the only reference to them is the weak reference in the map.
This is often useful for cache implementations since the map can be allowed to grow without bound and the garbage collector can be relied on to clean it up as necessary. One must be careful, though, when accessing entries since they can be collected at any time until there is a strong reference to the key.
cache = References::WeakKeyMap.new obj = MyObject.find_by_whatever obj_info = Service.lookup_object_info(obj) cache[obj] = Service.lookup_object_info(obj) cache[obj] # The values looked up from the service obj = nil ObjectSpace.garbage_collect cache.keys # empty array since the keys and values have been reclaimed
See AbstractReferenceKeyMap for details.
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