Having problems with my instance variable

ruby-talk
1

I'm sorry if this question seem stupid, but couldn't find it in the books.

I have this code in the models directory:
class Figure
  attr_reader :xpos, :ypos

  def initialize
    @xpos = 0
    @ypos = 0
    @other = 0
    @another = 0
  end

  def some
     call_other(@xpos,@ypos)
  end

  def more
     call_other(@other,@another)
  end

  def call_other(var1, var2)
    max = 9
    var1= rand(max)
    var2=rand(max)
  end
end

And have this on my controller:

  def figure
    fig = Figure.new
    fig.some
    render :text => "<h1>new values</h1>"+fig.xpos.to_s+" "+fig.ypos.to_s
  end

Problem is, it always print 0 0... as if the random wouldn't work, but I
have test the random outside this method (calling it in the first method,
not the second one), but the second method is one I need cos I use it too
many times and with different instance variables

Any help?

2

It's not clear to me what you're trying to do here. You want a method that
will set arbitrary variables to random numbers? That's a wild guess. What
you're actually doing when you call call_other is passing it the values in
@xpos and @ypos (which is 0 and 0 initially). Then, in call_other, you're
taking those 0s in with var1 and var2. Then you're over-writing var1 and
var2 with random numbers (0s are lost, as far as this method is concerned)
and then... you exit. You're leaving your @vars untouched because you're
passing the values, not the variables themselves.

If "max" is always going to be the same, I'd make it a constant at the class
level and then just have some look like this:

def some
  @xpos = rand MAX
  @ypos = rand MAX
end

If max won't be the same all the time, make a method that figures it out and
returns a random number based on it... An example will make more sense,
maybe.

def some
  @xpos = generate_random
  @ypos = generate_random
end

def generate_random
  max = 9 # or whatever determines your max value
  rand(max)
end

I hope that's clear. Scope can be confusing sometimes. If I am too rambly (I
hear that a lot), maybe someone with more experience will be more clear,
too.

Ben

···

On Feb 4, 2008 8:14 PM, macaco <macacoangel@gmail.com> wrote:

def some
    call_other(@xpos,@ypos)
end

def more
    call_other(@other,@another)
end

def call_other(var1, var2)
   max = 9
   var1= rand(max)
   var2=rand(max)
end
end

3

def some
    call_other(@xpos,@ypos)
end

def more
    call_other(@other,@another)
end

This worked:
class Test
  attr_reader :xpos

  def initialize
    @xpos = 0
  end

  def some
    p "before call: #{@xpos}"
    #notice the colon
    c :@xpos
    p "after call: #{@xpos}"
  end

  def call_other(var)
    max = 9
    self.instance_variable_set(var, rand(max))
  end
end

begin
  t = Test.new
  t.some
end

wyz@local ~ $ ruby test.rb
"before call: 0"
"after call: 7"

wyz@local ~ $ ruby test.rb
"before call: 0"
"after call: 2"

Warning: I'm not feeling well and the NyQuil is kicking in... :confused:

···

--
Andrew Stone

4

Thanks Day, but this is just a simplification of what I need

@Andrew Stone, thanks instance_variable_set makes it's work, but what if i
need the data inside too... for example

def call_other(var1,var2)
  max = 8
  if(var1 == 0)
    var1 = rand max
  else
    var1 += max
  end
  var2 = rand max
end

BTW, can you explain the line of code "c :@xpos", didn't get it

Thanks again

···

On Feb 4, 2008 11:03 PM, Andrew Stone <stonelists@gmail.com> wrote:

> def some
> call_other(@xpos,@ypos)
> end
>
> def more
> call_other(@other,@another)
> end
>

This worked:
class Test
attr_reader :xpos

def initialize
   @xpos = 0
end

def some
   p "before call: #{@xpos}"
   #notice the colon
   c :@xpos
   p "after call: #{@xpos}"
end

def call_other(var)
   max = 9
   self.instance_variable_set(var, rand(max))
end
end

begin
t = Test.new
t.some
end

wyz@local ~ $ ruby test.rb
"before call: 0"
"after call: 7"

wyz@local ~ $ ruby test.rb
"before call: 0"
"after call: 2"

Warning: I'm not feeling well and the NyQuil is kicking in... :confused:

--
Andrew Stone

5

I think instance_variable_get? Check out RDoc Documentation and
look in the right column for methods that start with instance_v. Or do a
find on _variable and see what turns up.

Ben

···

On Feb 5, 2008 11:37 AM, macaco <macacoangel@gmail.com> wrote:

@Andrew Stone, thanks instance_variable_set makes it's work, but what if i
need the data inside too...