# Dynamically call object instances **URL:** \ **Category:** Rails\ **Created:** [September 11, 2009, 9:50pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367 "2009-09-11T21:50:43Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![snantz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@snantz](https://www.ruby-forum.com/u/snantz)\ **Post date:** [September 11, 2009, 9:50pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367/1 "2009-09-11T21:50:43Z")
Hi again, I have these functions - about five of them - and they are all the exact same code except for which object instances they are referencing. For example, if I have a user object and each user can modify one of five phone fields - home, work, cell, etc. - I would like to call one function and just pass a varibale indicating which one I am modifying. I tried something like the following with no luck: def change\_phone(variable) … @user."#{varibale}" = @phone end where variable was work, for example. But it throws an error “Unexpected STRING\_BEG”. If there a way to do what I am doing? Thanks, -S ---
**Author:** ![snantz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@snantz](https://www.ruby-forum.com/u/snantz)\ **Post date:** [September 11, 2009, 10:05pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367/2 "2009-09-11T22:05:04Z")
Hi – On Fri, 11 Sep 2009, Shandy N. wrote: > def change\_phone(variable) > … > @user.“#{varibale}” = @phone > end > > where variable was work, for example. But it throws an error “Unexpected > STRING\_BEG”. If there a way to do what I am doing? Thanks, Yes: @user.send(“#{variable}=”, @phone) David – David A. Black | training Ruby Power and Light, LLC | consulting [http://www.rubypal.com](http://www.rubypal.com) | mentoring book: “The Well-Grounded Rubyist” | code review [The Well-Grounded Rubyist](http://www.manning.com/black2) | manuscript review ---
**Author:** ![snantz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@snantz](https://www.ruby-forum.com/u/snantz)\ **Post date:** [September 14, 2009, 7:51pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367/3 "2009-09-14T19:51:23Z")
What if I wanted to use that passed in variable to check and see if the field was blank or simple reference the value that that field held and not assign it a value? For example: if @user."#{params[:variable]}".blank? … end where params[:variable] = “home\_phone”. I would want that to translate to @user.home\_phone.blank? Is there a way to do that? Thanks in advance, -S ---
**Author:** ![snantz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@snantz](https://www.ruby-forum.com/u/snantz)\ **Post date:** [September 14, 2009, 8:54pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367/4 "2009-09-14T20:54:31Z")
Marnen Laibow-Koser wrote: > Well, the send() syntax that David mentioned would work for that, but if > @user is an ActiveRecord object, then you can also pretend it’s a hash > and do @user[params[:variable]] . Thanks for the reply, your suggestion did indeed work. > The fact that you’re asking these questions indicates that you need to > review your basic Ruby and Rails topics. These are elementary > questions. And the last time I checked this forum was open to anybody that wanted to ask a legitimate RoR question - noobie or otherwise - and while I will admit that I am no ruby expert I am far from a noobie. I have answered many questions for beginners of this forum without pointing out that “[t]hese are elementary questions” or saying that “you need to review your basic Ruby and Rails topics.” I have done this because I was once where many people who come to this forum are - without a clue in the world and simply trying to better my skill set in the programming field by trying to learn something knew, and, in my opinion, pretty freakin’ cool. Moreover, I have found this forum extremely helpful and an extremely valuable resource because I have felt comfortable to ask questions that I didn’t know the answer to - beginner or no - without people openly degrading me or other people by saying. . . well, what you said in your reply. If I had ever thought that for one moment, that somebody was asking a question that anybody who had read the first 5 pages of a beginning RoR book should, you know what, I kept it to myself. ---
**Author:** ![snantz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@snantz](https://www.ruby-forum.com/u/snantz)\ **Post date:** [September 14, 2009, 11:25pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367/5 "2009-09-14T23:25:50Z")
Shandy N. wrote: > Hi again, > > I have these functions - about five of them - and they are all the exact > same code except for which object instances they are referencing. For > example, if I have a user object and each user can modify one of five > phone fields - home, work, cell, etc. - I would like to call one > function and just pass a varibale indicating which one I am modifying. This is not a direct answer to your question since the answer has already been provided. But, I just wanted to point out that you might be struggling with this because your model breaks the First Normal Form (1NF) of database design, which states that a table should contain no repeating groups. In this case the repeating groups would be home\_phone, work\_phone cell\_phone, etc. These are all phone numbers making up a repeating group and should, technically, be normalized, which also cleanly solves the problem at hand. phones id | person\_id | label | number 1 | 1 | home | 555-123-1234 2 | 1 | work | 555-123-2345 ---
**Author:** ![snantz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/c2a13f/32.png) [@snantz](https://www.ruby-forum.com/u/snantz)\ **Post date:** [September 14, 2009, 8:15pm UTC](https://www.ruby-forum.com/t/dynamically-call-object-instances/175367/6 "2009-09-14T20:15:02Z")
Shandy N. wrote: > What if I wanted to use that passed in variable to check and see if the > field was blank or simple reference the value that that field held and > not assign it a value? > > For example: > > if @user.“#{params[:variable]}”.blank? > … > end > > where params[:variable] = “home\_phone”. I would want that to translate > to @user.home\_phone.blank? Is there a way to do that? Well, the send() syntax that David mentioned would work for that, but if @user is an ActiveRecord object, then you can also pretend it’s a hash and do @user[params[:variable]] . The fact that you’re asking these questions indicates that you need to review your basic Ruby and Rails topics. These are elementary questions. > Thanks in advance, > > -S ## Best, Marnen Laibow-Koser [http://www.marnen.org](http://www.marnen.org) removed\_email\_address@domain.invalid