# Attr\_writer vs attr\_accessor **URL:** \ **Category:** ruby-talk\ **Created:** [26 February 2008 08:29 UTC](https://rubytalk.org/t/attr-writer-vs-attr-accessor/44772 "2008-02-26T08:29:55Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Sunil\_Chikkegowda](https://avatars.discourse-cdn.com/v4/letter/s/edb3f5/32.png) [@Sunil\_Chikkegowda](https://rubytalk.org/u/Sunil_Chikkegowda)\ **Post date:** [26 February 2008 08:29 UTC](https://rubytalk.org/t/attr-writer-vs-attr-accessor/44772/1 "2008-02-26T08:29:55Z")
Hello all, From readings I understood that attr\_accessor is the one which has the property of attr\_reader and attr\_writer. If we define a variable as attr\_writer, we can use it to read and write as well. My question is; why do we need to use attr\_accessor since attr\_writer does the job of read and write? -Sunil ---
**Author:** ![Thomas\_Wieczorek](https://avatars.discourse-cdn.com/v4/letter/t/e47c2d/32.png) [@Thomas\_Wieczorek](https://rubytalk.org/u/Thomas_Wieczorek)\ **Post date:** [26 February 2008 09:38 UTC](https://rubytalk.org/t/attr-writer-vs-attr-accessor/44772/2 "2008-02-26T09:38:01Z")
Did you try it? I get an error, when I use the following irb(main):001:0\> class Foo irb(main):002:1\> attr\_writer :bar irb(main):003:1\> def initialize irb(main):004:2\> @bar = "hallo" irb(main):005:2\> end irb(main):006:1\> end =\> nil irb(main):007:0\> Foo.new.bar NoMethodError: undefined method `bar' for #\         from (irb):7 irb(main):008:0\> attr\_writer just creates the bar=(value) method, no bar() method to access the attribute. > **···** > > On Tue, Feb 26, 2008 at 9:29 AM, ycsunil \ wrote: > > > Hello all, > > > > From readings I understood that attr\_accessor is the one which has the > > property of attr\_reader and attr\_writer. If we define a variable as > > attr\_writer, we can use it to read and write as well. My question is; > > why do we need to use attr\_accessor since attr\_writer does the job of > > read and write? ---
**Author:** ![7stud](https://avatars.discourse-cdn.com/v4/letter/7/57b2e6/32.png) [@7stud](https://rubytalk.org/u/7stud)\ **Post date:** [26 February 2008 09:44 UTC](https://rubytalk.org/t/attr-writer-vs-attr-accessor/44772/3 "2008-02-26T09:44:38Z")
Sunil Chikkegowda wrote: > Hello all, > > If we define a variable as > attr\_writer, we can use it to read and write as well. Prove it. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Sunil\_Chikkegowda](https://avatars.discourse-cdn.com/v4/letter/s/edb3f5/32.png) [@Sunil\_Chikkegowda](https://rubytalk.org/u/Sunil_Chikkegowda)\ **Post date:** [26 February 2008 10:09 UTC](https://rubytalk.org/t/attr-writer-vs-attr-accessor/44772/4 "2008-02-26T10:09:57Z")
Thanks! for clearing the doubt with an example. In general I thought; if varialbe can be writable then it should hold property of readable... which is not true in attr\_writer. > **···** > > On Feb 26, 2:38 pm, Thomas Wieczorek \ wrote: > > > On Tue, Feb 26, 2008 at 9:29 AM, ycsunil \ wrote: > > \> Hello all, > > > > \> From readings I understood that attr\_accessor is the one which has the > > \> property of attr\_reader and attr\_writer. If we define a variable as > > \> attr\_writer, we can use it to read and write as well. My question is; > > \> why do we need to use attr\_accessor since attr\_writer does the job of > > \> read and write? > > > > Did you try it? I get an error, when I use the following > > > > irb(main):001:0\> class Foo > > irb(main):002:1\> attr\_writer :bar > > irb(main):003:1\> def initialize > > irb(main):004:2\> @bar = "hallo" > > irb(main):005:2\> end > > irb(main):006:1\> end > > =\> nil > > irb(main):007:0\> Foo.new.bar > > NoMethodError: undefined method `bar' for #\ > > from (irb):7 > > irb(main):008:0\> > > > > attr\_writer just creates the bar=(value) method, no bar() method to > > access the attribute. ---
**Author:** ![Jesus\_Gabriel\_y\_Gala](https://avatars.discourse-cdn.com/v4/letter/j/96bed5/32.png) [@Jesus\_Gabriel\_y\_Gala](https://rubytalk.org/u/Jesus_Gabriel_y_Gala)\ **Post date:** [26 February 2008 11:10 UTC](https://rubytalk.org/t/attr-writer-vs-attr-accessor/44772/5 "2008-02-26T11:10:50Z")
attr\_xxx do not "declare" any property or type of property. They just generate methods. attr\_reader :xxx generates a method that returns the value of the instance variable @xxx attr\_writer :xxx generates a method xxx= that sets the value of the instance variable @xxx attr\_accessor :xxx generates the two above methods. Hope this helps, Jesus. > **···** > > On Tue, Feb 26, 2008 at 11:09 AM, ycsunil \ wrote: > > > On Feb 26, 2:38 pm, Thomas Wieczorek \ wrote: > > \> On Tue, Feb 26, 2008 at 9:29 AM, ycsunil \ wrote: > > \> \> Hello all, > > \> > > \> \> From readings I understood that attr\_accessor is the one which has the > > \> \> property of attr\_reader and attr\_writer. If we define a variable as > > \> \> attr\_writer, we can use it to read and write as well. My question is; > > \> \> why do we need to use attr\_accessor since attr\_writer does the job of > > \> \> read and write? > > \> > > \> Did you try it? I get an error, when I use the following > > \> > > \> irb(main):001:0\> class Foo > > \> irb(main):002:1\> attr\_writer :bar > > \> irb(main):003:1\> def initialize > > \> irb(main):004:2\> @bar = "hallo" > > \> irb(main):005:2\> end > > \> irb(main):006:1\> end > > \> =\> nil > > \> irb(main):007:0\> Foo.new.bar > > \> NoMethodError: undefined method `bar' for #\ > > \> from (irb):7 > > \> irb(main):008:0\> > > \> > > \> attr\_writer just creates the bar=(value) method, no bar() method to > > \> access the attribute. > > > > Thanks! for clearing the doubt with an example. In general I thought; > > if varialbe can be writable then it should hold property of > > readable... which is not true in attr\_writer.