An example of using WeakRef for caching data
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require 'weakref' | |
class TransientCache < Hash | |
class AmbivalentRef < WeakRef | |
def __getobj__ | |
super rescue nil | |
end | |
end | |
def []= key, object | |
super(key, AmbivalentRef.new(object)) | |
end | |
def [] key | |
ref = super(key) | |
self.delete(key) if !ref.weakref_alive? | |
ref | |
end | |
end | |
# Here is a silly little example: | |
if __FILE__ == $0 | |
## Sample usage | |
c = TransientCache.new | |
x = "important" | |
c[:a] = "Hello" | |
c[:b] = Object.new | |
c[:x] = x | |
# Lets see what was in the cache | |
puts c[:a].inspect | |
puts c[:b].inspect | |
puts c[:x].inspect | |
# Force garbage collection. | |
# This will collect the weak-refs that are no longer within scope. | |
# This doesn't guarantee they are removed though. | |
puts "*** Garbage Collection ***" | |
ObjectSpace.garbage_collect | |
puts c[:a].inspect | |
puts c[:b].inspect | |
puts c[:x].inspect | |
end |
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