Code error on Lesson 9 in Tutorial

[spamcatcher]

If anyone is using the tutorial pages Lesson 9 has an omission

https://sites.google.com/a/ruby4kids.com/gosu/lesson-9

 

Where you pass the @player.laser to the bullet update method (approx line 31 in Window code) as noted in the comments, this will fail unless you add the laser value to the Player class as such:

 

class Player

attr_reader :lives, :x, :y, :laser

.

.

.

 

hope this helps.

[Mark]

It still fails - now with "wrong number of arguments (1 for 0)"

hmmm

I don't see how the live_bullets call works here - or how to fix it.

[Alberto Morales]

Can you send the snippet of your code to see how you are using live_bullets.

Alberto.

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[Mark]

Thanks Alberto

 

class Window < Gosu::Window

....

  def run_game
    live_bullets.each {|bullet| bullet.update(@player.laser)}
    @player.update
  end

 

  def live_bullets
    @bullets.select{|bullet| bullet.alive == true}
  end
...

end

 

and

 

class Bullet
  attr_reader :x, :y, :alive, :laser

...

  def update
    @y=@y+10
    if @y>@window.width
      @y=0
      @x=rand(@window.width)
    end
    hit_by?(laser)
  end

...

end

 

 

The Player class doesn't have a .laser method.

Adding :laser to the attr_reader in the Player class confuses the program because it now expects @player.laser to be a variable but is not expecting a variable to be passed to the bullet.update method (the laser variable in the "hit_by?(laser)" call is dragged into Bullet by attr_reader).

 

So I'm a bit confused, and my program is too.

 

I'm wondering if it has to do with the "bullet" words: the Window class now has a number of "bullets" defined as

@bullets = 2.times.map {Bullet.new(self)}

but no definition of "bullet" (single and lowercase) - could it be that I need to change the calls such as

 live_bullets.each {|bullet| bullet.update(@player.laser)}
to reflect this?

 

Thanks so much for your help.

 

Mark

[Mark]

Ok - so that last bit shows that I didn't understand the syntax of the .each or .select methods for an array.

I realise now that

>>  live_bullets.each {|bullet| bullet.update(@player.laser)}

is defining a temporary object 'bullet' to hold the result of the .each call, or something like that.

 

I've got it now - I've missed out the (laser) argument for the definition of the bullet.update method. So it does work by adding :laser to the attr_reader after all.

Sorry to bother you.

 

Mark