After comments by Mike H-R and Stefan to a question of mine, I noticed that ObjectSpace.each_object(String) includes just about any string I can think of:
strings = ObjectSpace.each_object(String)
strings.include?("some random string") # => true
or
strings = ObjectSpace.each_object(String).to_a
strings.include?("some random string") # => true
I thought that strings should include only strings that existed at that point. Why does it include just about any string?
Yet, when I count the length of strings, it returns a finite number:
ObjectSpace.each_object(String).to_a.length # => 15780
This is observed on Ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-linux] interpreter and irb.
Does this have anything to do with frozen string literal optimization introduced in Ruby 2.1?
When writing code in the IRB strings are added to the ObjectSpace as they are typed:
strings = ObjectSpace.each_object(String)
strings.include?("some random string") # => true
strings = ObjectSpace.each_object(String).to_a
strings.include?("some other random string") # => false
When trying to do it inside an rb file, the text is already there, because it is added when the file is parsed.
test.rb
strings = ObjectSpace.each_object(String)
strings.include?("some random string") # => true
strings = ObjectSpace.each_object(String).to_a
strings.include?("some other random string") # => true
strings = ObjectSpace.each_object(String).to_a
strings.include?("some other random string " + "dynamically built") # => false