Very simple demonstration of NSHashTable in RubyMotion

cache.rb

class MyObject
  attr_accessor :my_id

  def isEqual(object)
    object.class == self.class && object.my_id == my_id
  end
	
  def hash
    my_id.hash
  end
end

cache = NSHashTable.alloc.initWithOptions(NSPointerFunctionsWeakMemory | NSPointerFunctionsObjectPersonality, capacity:0)
my_object = MyObject.new
my_object.my_id = 123 
cache.addObject(my_object)

p my_object
# => #<MyObject:0x7f9cf94b80e0 @my_id=123>



other_object = MyObject.new
other_object.my_id = 123 

cached_object = cache.member(other_object)

p cached_object
# => #<MyObject:0x7f9cf94b80e0 @my_id=123>

p cache.allObjects 
# => [#<MyObject:0x7f9cf94b80e0 @my_id=123>]