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I need to occasionaly create images with rmagick in a cache dir.
To then get rid of them fast, without loosing them for the view, I want to delete the image-files while my Ruby Instance of the Image-Class get's destructed or enters the Garbage Collection.
What ClassMethod must I overwrite to feed the destructor with code?
378
Destructors are usually used to deallocate memory and do other cleanup for a class object and its class members when the object is destroyed. A destructor is called for a class object when that object passes out of scope or is explicitly deleted.
Destructors are called when one of the following events occurs: A local (automatic) object with block scope goes out of scope. An object allocated using the new operator is explicitly deallocated using delete . The lifetime of a temporary object ends.
There are specific rules that make an overloaded delete function a destructor function: the function must have just one input argument, which is an object of the class, and it must not have any output arguments.
It never takes any parameters, and it never returns anything. You can't pass parameters to the destructor anyway, since you never explicitly call a destructor (well, almost never).
@edgerunner's solution almost worked. Basically, you cannot create a closure in place of the define_finalizer call since that captures the binding of the current self. In Ruby 1.8, it seems that you cannot use any proc object converted (using to_proc) from a method that is bound to self either. To make it work, you need a proc object that doesn't capture the object you are defining the finalizer for.
class A FINALIZER = lambda { |object_id| p "finalizing %d" % object_id } def initialize ObjectSpace.define_finalizer(self, self.class.method(:finalize)) # Works in both 1.9.3 and 1.8 #ObjectSpace.define_finalizer(self, FINALIZER) # Works in both #ObjectSpace.define_finalizer(self, method(:finalize)) # Works in 1.9.3 end def self.finalize(object_id) p "finalizing %d" % object_id end def finalize(object_id) p "finalizing %d" % object_id end end a = A.new a = nil GC.start If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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