Re: attr_reader - general question

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On Tue, Feb 1, 2011 at 7:11 PM, Jim Carter <jcarter / leupold.com> wrote: > I have the following configuration: > > class ExternalBallistics > > =A0 =A0attr_accessor =A0 =A0:a,:b =A0 #inputs > =A0 =A0attr_reader =A0 =A0 =A0:c =A0 =A0 =A0#outputs > > =A0 =A0def initialize(&block) > =A0 =A0 instance_eval &block > =A0 =A0end > > =A0 =A0def calculate > =A0 =A0 =A0 c =3D a + b This is not calling the method "c=3D", not that you have one, in any case. "c" is considered a local variable. Change it to: @c =3D a + b to set the value in the instance variable that your reader will access. > =A0 =A0end > > end #class > > > > ExternalBallistics.new do > > =A0 self.a =3D 5 > =A0 self.b =3D 3 > > =A0 calculate > > =A0 puts self.c > > end #ExternalBallistics > > > This returns a nil value for c. =A0If I use "puts" inside of def > calculate, I will get 8 for an answer. =A0Why does a and b act globally > and c not. =A0Am I forced to use a return on calculate to get an answer. > If I do so, do I still need to define an attr_reader :c (what use is it > then) ? > > > Thanks Jesus.