Implementation of a map in which soft references are kept to the map values. This allows the garbage collector to reclaim these objects if the only reference to them is the soft 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 the values can be collected at any time until there is a strong reference to them.
cache = References::SoftValueMap.new foo = "foo" cache["strong"] = foo # add a value with a strong reference cache["soft"] = "bar" # add a value without a strong reference cache["strong"] # "foo" cache["soft"] # "bar" ObjectSpace.garbage_collect ObjectSpace.garbage_collect cache["strong"] # "foo" cache["soft"] # nil
See AbstractReferenceValueMap for details.
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