Question

Just wondering why

def move
  world_switch(@pos_X += 1, @pos_X -= 1, @pos_Y += 1, @pos_Y -= 1)
end

  def world_switch(do_on_north, do_on_south, do_on_east, do_on_west)
    case @facing # => 'NORTH'
    when 'NORTH'
      puts do_on_north # => 1
      do_on_north
    when 'SOUTH'
      do_on_south
    when 'EAST'
      do_on_east
    when 'WEST'
      do_on_west
    end
  end

Calling world_switch:

robot = Robot.new(0, 0, 'NORTH')
robot.move
puts robot.instance_variable_get("@pos_X") #=> 0

results in changing nothing, I would like to increase or decrease instance variable @pos_X or @pos_Y

This is my initialize method

def initialize(pos_X, pos_Y, facing)
    @pos_X, @pos_Y, @facing = pos_X, pos_Y, facing
  end

and that’s how I create an instance of the class robot = Robot.new(0, 0, 'NORTH')

All help will be appreciated

Answer 1

The explanation for the current behaviour is as Chowlett described, but did you intend for your @pos_X += 1, @pos_X -= 1 etc in move to be blocks of code and then for exactly one of these to be called from world_switch depending on which way the robot is facing?

If so, move needs to be declared like this

def move
  world_switch(Proc.new { @pos_X += 1 }, Proc.new { @pos_X -= 1 },
    Proc.new { @pos_Y += 1 }, Proc.new { @pos_Y -= 1 })
end

and then in world_switch you can do something like

case @facing # => 'NORTH'
    when 'NORTH'
      do_on_north.call
    when 'SOUTH'
      do_on_south.call
 ...