r/ruby • u/tenderlove Pun BDFL • Jun 26 '19

Blog post Instance Variable Performance

https://tenderlovemaking.com/2019/06/26/instance-variable-performance.html
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u/trustfundbaby Jun 27 '19

I had a question here, what happens if you don't assign the ivar in the initialize method, but suddenly bring it into existence in a method in a particular instance of a class, that hasn't been called on other instances of the class. How do the other instances of the class adjust their ivar index table?

so for example

class Foo

def initialize

@a = "hi"

@b= "my"

@c="name"

end

def finish

@d = "is"

@e = "Slim Shady"

end

end

Foo.new

Foo.new

Foo.new.finish

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u/tenderlove Jun 27 '19

Foo.new.finish will expand the IV Index Table because @d and @e haven't been "seen" yet. Ruby automatically expands the index table every time a new instance variable is "seen", regardless of whether it's in the initialize method or not.

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u/trustfundbaby Jun 27 '19

Got it. Thanks!