I now extend the class by adding a method, which makes use of an instance
variable which previously did not exist.

How can I make it test that the instance variable is uninitialised, so I can
prevent a warning? This is what I am trying to do:

  class Foo
    attr_reader :things
    def add_thing(n)


      end

    end
  end

if ruby is running with -w. (This is 1.6.8)

I am hoping that I don't have to keep track of all existing Foo objects,
just so that I can send them a message 'reset_things'

Thanks...

Brian.

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else

end

Phil

    def add_thing(n)


    end

--
matt

HTH,

Bill

Thanks to everyone.

B.

I have a Struct, and have dynamically added a new member.

I want to check whether the instance variable corresponding to that
attribute is already initialised. How can I do that? Example:

  foo = Struct.new("Foo", "a", "b", "c")
  obj = foo.new

  newmember="d"
  foo.module_eval { attr_accessor newmember }

  obj.send("#{newmember}=", []) if obj.send(newmember).nil?    # ***
  obj.send(newmember)<< "hello"
  puts obj.send(newmember)

How can I write the line '***' so it does not generate a warning under -w ?
Note that 'respond_to?' is not the answer, because the accessor methods do
exist - it's just the associated instance variable which has not been
initialised.

Cheers,

Brian.

B> I want to check whether the instance variable corresponding to that
B> attribute is already initialised.

 First test if the instance variable exist.

Guy Decoux

In message "Re: How to test for existence of instance variable?"

|How can I write the line '***' so it does not generate a warning under -w ?

Attribute readers should not report warning for uninitialized instance
variables.  I will fix.

                                                        matz.

(since all I'm trying to do is avoid a warning).

Regards,

Brian.

B> That was essentially what I was asking. What is the way to check if an
B> instance variable exists, when its name is dynamic? Preferably not something
B> incredibly inefficient like

 #instance_variables give you the name of all instance variables for an
 object.

Guy Decoux

Paul

In message "Re: How to test for existence of instance variable?"

|> |How can I write the line '***' so it does not generate a warning under -w ?
|>
|> Attribute readers should not report warning for uninitialized instance
|> variables.  I will fix.
|
|Why should this be fixed?  The warning looks reasonable to me.

Because it's non intuitive.  There's no logical relationship between

users.

                                                        matz.

Hal