# Strange question: Convert string to array name **URL:** \ **Category:** Ruby\ **Created:** [February 20, 2007, 1:21am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119 "2007-02-20T01:21:18Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 1:21am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/1 "2007-02-20T01:21:18Z")
I am coming to Ruby from LISP where I was more competent when it came to symbol manipulation 🙂 I have spent some time trying to solve this problem and figure it’s my general lack of deep knowledge ala Ruby that keeps me from seeing an “easy” solution. With that said, I apologize if this has been answered and I missed it. I have a string in a variable. foo = “bobo” I want to use foo to access an array called bobo. I will have bobo defined already. Is there a way to do this? Take foo and use it to access bobo[2], for example. I thought about turning foo into a symbol, but that wasn’t the way. And, I think there should be a way to ask Ruby to return an object via its string name, but I am missing the way. any advice would be appreciated. kenny ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 1:57am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/2 "2007-02-20T01:57:20Z")
I’m still pretty much a newbie, but my first thought that works is: eval(‘bobo’)[2] -Stephen ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 2:10am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/3 "2007-02-20T02:10:20Z")
On Feb 19, 7:59 pm, Aaron P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ## irb(main):001:0\> awesome\_array = %w{ one two three four five } > > Aaron P.[http://tenderlovemaking.com/-](http://tenderlovemaking.com/-) Hide quoted text - > > - Show quoted text - Thanks for the folks that mentioned eval—I thought of that after the posting but assumed that, as in LISP, there might be a better way to accomplish it 🙂 It’s nice to see more similarities between LISP and Ruby. kenny ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 2:47am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/4 "2007-02-20T02:47:23Z")
There should be, also I don’t remember it. For all kinds of variables except for local I know the ways, but local elludes me 🙂 Aur S. PLUG: [http://rubymentor.rubyforge.org/wiki/wiki.pl](http://rubymentor.rubyforge.org/wiki/wiki.pl) ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 3:12am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/5 "2007-02-20T03:12:24Z")
On Feb 19, 2007, at 8:10 PM, kenbo wrote: > Thanks for the folks that mentioned eval—I thought of that after the > posting but assumed that, as in LISP, there might be a better way > to accomplish > it 🙂 > > It’s nice to see more similarities between LISP and Ruby. I don’t know whether or not you will think this better than using ‘eval’, but in Ruby this kind of indirect reference problem can often be handled by introducing a hash. For example, ` a = %w{ one two three four five } b = %w{ six seven eight nine } h = {} h['a'] = a h['b'] = b foo = 'a' h[foo][2] # => "three" foo = 'b' h[foo][2] # => "eight" ` Regards, Morton ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 3:15am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/6 "2007-02-20T03:15:24Z")
On Feb 19, 2007, at 7:20 PM, kenbo wrote: > I want to use foo to access an array called bobo. I will have bobo > defined already. This type of question seems to come up periodically on the list but I never seem to run into in while coding. I tend to think that in most (but not all) cases the need to reach for eval indicates some larger design issue. In your case, I would ask why you are resorting to using several local variables that you need to distinguish by name rather than simply using a hash to organize things? arrays = {} array[:bobo] = [1,2,3] array[:foo] = [4,5,6] array[:foo][2] # 5 Perhaps if you gave the list the ‘bigger’ picture they could suggest a solution that doesn’t require ‘eval’. Gary W. ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 11:11am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/7 "2007-02-20T11:11:07Z")
On 2/20/07, SonOfLilit [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > On Feb 19, 7:59 pm, Aaron P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > > > > > > it. > > > > > > – > > > Aaron P.[http://tenderlovemaking.com/-](http://tenderlovemaking.com/-) Hide quoted text - > > > > > > - Show quoted text - > > > > Thanks for the folks that mentioned eval—I thought of that after the > > posting but > > assumed that, as in LISP, there might be a better way to accomplish > > it 🙂 > > Are you thinking about Ma\*\*\*\*, do not mention it anymore on this list 😉 > > Well it is not really the way of Ruby. > > > > It’s nice to see more similarities between LISP and Ruby. > > > > kenny There is if you can get away from the local variable as somebody mentioned without sharing his wisdom with us 😉 If we want to access an array @bobo there is instance\_variable\_get( “@'” \<\< foo.to\_s ).first and all kind of variations. Cheers Robert ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 2:00am UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/8 "2007-02-20T02:00:20Z")
On Tue, Feb 20, 2007 at 09:20:13AM +0900, kenbo wrote: > I have a string in a variable. > foo = “bobo” > > I want to use foo to access an array called bobo. I will have bobo > defined already. > > Is there a way to do this? eval() might be what you’re looking for. You can use eval to return the array then index in to it. Here’s an example from: irb(main):001:0\> awesome\_array = %w{ one two three four five } =\> [“one”, “two”, “three”, “four”, “five”] irb(main):002:0\> foo = ‘awesome\_array’ =\> “awesome\_array” irb(main):003:0\> puts eval(foo)[1] two =\> nil irb(main):004:0\> Hope that helps! ---
**Author:** ![kenbo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/e9c0ed/32.png) [@kenbo](https://www.ruby-forum.com/u/kenbo)\ **Post date:** [February 20, 2007, 12:23pm UTC](https://www.ruby-forum.com/t/strange-question-convert-string-to-array-name/86119/9 "2007-02-20T12:23:33Z")
It’s very unusual to need to dynamically reference a local variable. In Ruby, local variables usually are highly, er, localized. An instance variable is much more frequently used in the way you describe, and you can access it, as Robert says, like so: > > @foo = “the value” > > =\> “the value” > > > name = “foo” > > =\> “foo” > > > instance\_variable\_get("@#{name}") > > =\> “the value” Evan W.