From: Joshua Abbott <joshnabbott@...>
Date: 2009-01-01T13:51:26+09:00
Subject: Re: How do I pass the name of an instance variable into an o

Glenn,

There may be a much better way to do this, but here's what I threw 
together:

class SomeClass
  attr_accessor :a, :b
  def initialize
    @a = 'A'
    @b = 'B'
  end

  def print_instance_variable(variable)
    if instance_variables.include?("@#{variable}")
      puts self.send("#{variable}")
    else
      raise 'Not an instance variable.'
    end
  end
end

x = SomeClass.new
x.print_instance_variable('a')

Hope that at least points you in the right direction.

-- Josh
http://iammrjoshua.com



Glenn wrote:
> Hi,
> 
> Suppose I wanted to create a method for an object that allowed me to 
> pass in the name of an instance variable and to perform some task on the 
> variable.  For the sake of simplicity, let's say that I'd like to be 
> able to print out the value of the specified instance variable.  Also, 
> I'd want the method to raise an exception if the name of the variable 
> getting passed into the object is not actually an instance variable in 
> the object.
> 
> The class would look something like this:
> 
> class SomeClass
>   def initialize
>     @a = 1
>     @b = 'xxx'
>   end
> 
>   def print_instance_variables(obj)
>      # some code goes here
>   end
> end
> 
> And here's how I'd like to be able to use it:
> 
> x = SomeClass.new
> x.print_instance_variables(:a) # writes the value of @a to the console
> x.print_instance_variables(:b) # writes the value of @b to the console
> x.print_instance_variables(:a, :b) # writes the values of @a and @b to 
> the console
> x.print_instance_variables(:z) # causes an exception because there is 
> no@z
> 
> Any suggestions would be greatly appreciated.
> 
> Thanks,
> 
> Glenn

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