Ruby: undefined local variable (NameError) -- but it is defined

Question

This is a part of my code for a Naughts and Crosses (tic-tac-toe) game.

positions = [" ", " ", " ", " ", " ", " ", " ", " ", " "]

# Returns .. 1 = Square already owned, 2 = Blank square, 0 = Enemy square
def check_square(side, square)
  if positions[square] == side
    state = 1
  elsif positions[square] == B
    state = 2
  else
    state = 0
  end
  return state
end

When I run the program I get the error:

in `check_square': undefined local variable or method `positions' for main:Object (NameError)

However it is literally defined right above it. I have ran the snippet of code in its own .rb and it works fine so I don't see why it doesn't work. I must assume it has to do with the scope of positions but, for me at least (beginner programmer), I don't see why it doesn't work here but does in its own program.

Any help is gladly appreciated.

sawa · Accepted Answer · 2015-12-24 19:29:35Z

1

A local variable's scope cannot cross a method definition. positions that is assigned outside of the method definition is not visible from within the method definition.

To make it visible, you can make it an instance variable, class variable, global variable, or constant, for example. Or, you can pass it as an argument to the method.

answered Dec 24, 2015 at 19:29

sawa

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4 Comments

Soviet Ketchup Over a year ago

Thank you, I have set it to a global variable and it now seems to work!

sawa Over a year ago

However, global variable is not recommended in object oriented programming.

Soviet Ketchup Over a year ago

what would you recommend I use instead?

sawa Over a year ago

instance variable or constant

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