Observe variable set and variable change

ruby-talk
1

Hey folks,

is there any kind of Ruby / C function with which it is possible to see when a variable is set or changed?

Something like:

class x

  def y()
    z = 42
    z = 100
  end
end

So that a function takes care about setting the 42 and another for caring about changing the value of z to 100?

thanks in advance

sala

2

Hey folks,

is there any kind of Ruby / C function with which it is possible to see when a variable is set or changed?

Something like:

class x

  def y()
    z = 42
    z = 100
  end
end

So that a function takes care about setting the 42 and another for caring about changing the value of z to 100?

thanks in advance

sala

···

saladin.mundi@gmx.de wrote:
--
RMagick: http://rmagick.rubyforge.org/

3

Let's try again...

There's Observable:

~$ ri Observable
------------------------------------------------------ Class: Observable
      Implements the Observable design pattern as a mixin so that other
      objects can be notified of changes in state. See observer.rb for
      details and an example.

···

saladin.mundi@gmx.de wrote:

Hey folks,

is there any kind of Ruby / C function with which it is possible to see when a variable is set or changed?

Something like:

class x

  def y()
    z = 42
    z = 100
  end
end

So that a function takes care about setting the 42 and another for caring about changing the value of z to 100?

thanks in advance

sala

------------------------------------------------------------------------

Instance methods:
      add_observer, changed, changed?, count_observers, delete_observer,
      delete_observers, notify_observers
~$

--
RMagick: http://rmagick.rubyforge.org/

4

is there any kind of Ruby / C function with which it is possible to see
when a variable is set or changed?

You can try trace_var (or whatever the name was)

trace_var :$x, proc{print "$x is now ", $x, "\n"}

···

--
Posted via http://www.ruby-forum.com/\.

5

You can try trace_var (or whatever the name was)

trace_var :$x, proc{print "$x is now ", $x, "\n"}

thanks guys. to trace_var
this as i see is just for tracing global vars. it would be great if there is a way for also tracing vars inside methods.

def x()
  z = 10
  z = 42
end

--> the variable z was initialized with the value 10
--> the variable z was changed with the value 42

6

unknown wrote:

a way for also tracing vars inside methods.

def x()
  z = 10
  z = 42
end

I don't think that there exists some method for this purpose. You can
use Ruby's trace possibilities or a simple method for looking at local
variables at special points...

def show_local_vars(bind, *d)
  puts '----- variables -----'
  vars = eval("local_variables", bind)
  (d.length == 0 ? vars : (d.map{|s|s.to_s} & vars)).each do |v|
    begin
      puts "#{v}=#{eval(v,bind)}"
    rescue
      puts "+++++ Variable '#{v}' not defined"
    end
  end
end

def x()
  z = 10
  show_local_vars(binding)
  z = 42
  show_local_vars(binding, :z, :a)
end

x

...outputs...

----- variables -----
z=10
----- variables -----
z=42

Wolfgang Nádasi-Donner

···

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Posted via http://www.ruby-forum.com/\.

7

I don't think that there exists some method for this purpose. You can
use Ruby's trace possibilities or a simple method for looking at local
variables at special points...

What methods does ruby itself [so, the C-core] uses to initialize a variable (local, global, instance, whatever)?
And what method(s) is(are) used to give an exisiting variable a new value?

thanks