Ruby method scope

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Ruby method scope convention

  • Ruby method not have a strict pass by value or pass by reference.
  • if you passing an argument, and the argument calls a method that mutates the caller which may or may not have a !, then it’s going to change that object.

This is very common source bug.

example

pass by value(not mutate argument in method):

a = [1, 2, 1]
def my_method(a)
  a.uniq
end
puts a

will produce:

1
2
1

pass by reference(mutate argument in method):

a = [1, 2, 1]
def my_method(a)
  a.uniq!
end
puts a

will produce:

1
2