From: Ralph Shnelvar <ralphs@...32.com>
Date: 2010-01-09T02:05:14+09:00
Subject: Something changed an instance variable ... and now I'm confused

Newbie here.

Consider this irb session ...


F:\InstantRails-2.0-win\rails_apps>irb
irb(main):001:0> class X
irb(main):002:1>   attr_accessor :x, :y
irb(main):003:1> end
=> nil
irb(main):004:0>
irb(main):005:0* x1 = X.new
=> #<X:0x29211a0>
irb(main):006:0>
irb(main):007:0* x1.x = 5;
irb(main):008:0* x1.y = 6;
irb(main):009:0*
irb(main):010:0*
irb(main):011:0*
irb(main):012:0* class X
irb(main):013:1>   def x=(arg)
irb(main):014:2>     puts "arg=" + arg.to_s
irb(main):015:2>     @x = arg
irb(main):016:2>     puts "whoopy"
irb(main):017:2>     @x
irb(main):018:2>   end
irb(main):019:1>
irb(main):020:1*   def make_x
irb(main):021:2>     self.x = "xyzzy"
irb(main):022:2>   end
irb(main):023:1> end
=> nil
irb(main):024:0>
irb(main):025:0*
irb(main):026:0* x1.x = "hello"
arg=hello
whoopy
=> "hello"
irb(main):027:0> x1
=> #<X:0x29211a0 @y=6, @x="hello">
irb(main):028:0> x1.make_x
arg=xyzzy
whoopy
=> "xyzzy"
irb(main):029:0> x1
=> #<X:0x29211a0 @y=6, @x="xyzzy">
irb(main):030:0>



The background ...

I am debugging an RoR application and noticed that the @activation_code instance variable was being modified _somewhere_.  I couldn't tell where.

So I added a method to the User class

  def activation_code=(arg)
    puts at_file_line_msg(__FILE__, __LINE__)
	  puts "arg=" + arg
    @activation_code=arg
    debugger
    @activation_code
  end


When I look at the value of @activation_code in the debugger (at the debuuger breakpoint), it has the right value ...

but when I look at self in the debugger, the activation_code field is nil.

I do not understand why things seem to work in the snippet of code I provided, above, in irb ... but do not work in the far more complex RoR environment.