Why does the else condition of my if-statement not work?

Question

I wrote a tic-tac-toe program. The problem I am experiencing is that in my if statement, which allows the user enter his/her desired coordinate, my else condition is not working. The else condition is in place in case the user enters a coordinate not on the board.

This is my code:

class Game

  def initialize
    @board=Array.new
    @board[1]="1  __|"
    @board[2]="__"
    @board[3]="|__"
    @board[4]="\n2  __|"
    @board[5]="__"
    @board[6]="|__"
    @board[7]="\n3    |"
    @board[8]="  "
    @board[9]="|  "
    @turn="o"
    @win_status = false
  end

  def turn
    @turn
  end

  def show_board
    puts "   1  2  3"
    @board.each do |i|
      print i
    end
    puts ""
  end

  def set_turn #switches turns
    if @turn == "x"
      @turn = "o"
    else @turn == "o"
      @turn = "x"
    end
  end

  def make_move
    puts "Enter x coordinate"
    x=gets.to_i
    puts "Enter y coordinate"
    y=gets.to_i
    if y==1 && x==1
      @board[1]="1  _"+@turn+"|"
    elsif y==2 && x==1
      @board[2]="_"+@turn
    elsif  y==3 && x==1
      @board[3]="|_"+@turn
    elsif y==1 && x==2
      @board[4]="\n2  _"+@turn+"|"
    elsif y==2 && x==2
      @board[5]="_"+@turn
    elsif y==3 && x==2
      @board[6]="|_"+@turn
    elsif y==1 && x==3
      @board[7]="\n3   "+@turn+"|"
    elsif y==2 && x==3
      @board[8]=" "+@turn
    elsif y==3 && x==3
      @board[9]="| "+@turn+" \n"
    else
      "You entered an invalid coordinate"
    end

  end

  def win_combo
    return [[@board[1][4] + @board[2][1] + @board[3][2]], [@board[4][5] + @board[5][1] + @board[6][2]], [@board[7][5] + @board[8][1] + @board[9][2]],[@board[1][4] + @board[4][5] + @board[7][5]], [@board[2][1] + @board[5][1] + @board[8][1]], [@board[3][2] + @board[6][2] + @board[9][2]], [@board[1][4] + @board[5][1] + @board[9][2]], [@board[3][2] + @board[5][1] + @board[7][5]]]
  end

  def check_win
    #if some row or column or diagonal is "xxx" or "ooo" then set @win_status = true
    self.win_combo.each do |arr|
      str = arr.join
      if str == "xxx"
        puts "X Wins!"
        return true
      elsif str == "ooo"
        puts "O Wins!"
        return true
      end
    end
    return false
  end
  g = Game.new
  while g.check_win != true
    g.show_board
    g.set_turn
    g.make_move
  end
end

Answer 1

You are just returning the string: "You entered an invalid coordinate".

I suspect that you want to display it using:

puts "You entered an invalid coordinate"

Otherwise it is passed as the result of g.make_move and then ignored.

Answer 2

I'm assuming you would like to print: "You entered an invalid coordinate" to the console in the event of an invalid x, y coordinate. You need to add a method to that statement like:

else
  puts "You entered an invalid coordinate"
end

Or:

else
  abort "You entered an invalid coordinate"
end

Answer 3

It looks you you forgot to use puts or print in front of your "You entered an invalid coordinate" string. As it is currently written it is returned from the method.

In Ruby, the return value of a method is the value returned by the last statement evaluated. For example, both of these methods will return the same value if x=3:

def square_example(x)
  if x ==3
    x_squared = 9
  end
end


def square_example2(x)
  if x == 3
    x_squared = 9
  end
  return x_squared
end

For simplicity of testing you might try using explicit returns so that you can easily tell what it is you are returning from the method. Or (as a beginner with Ruby myself) you could add in a puts statement with each if/else result so that you can easily monitor the results of each move and then remove those puts lines when you know everything is working properly.

Answer 4

Looks like this is a misinterpretation of the site below, but if you're interested in the difference between 'and' and '&&' you should check out the comments below. From: http://www.tutorialspoint.com/ruby/ruby_operators.htm

You will want to use "and" instead of "&&", an example:

if y==1 and x==1
    # do move
elsif y==2 and x==1
    # do move
.
.
.
else
    "invalid coordinate"
end

The "&&" operator will check that the values on either side of it are nonzero. If they are both nonzero then it will return true. In your case it is doing the operation

false && false

Where false != 0, so it returns true.

Here is another discussion of this: http://archive.railsforum.com/viewtopic.php?id=27353