# A very half-baked idea: setting local variables **URL:** \ **Category:** ruby-talk\ **Created:** [8 July 2013 21:06 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165 "2013-07-08T21:06:15Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [8 July 2013 21:06 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/1 "2013-07-08T21:06:15Z")
I'm sure this nonexistent feature is not in great demand, but there have been different times that I (and other people) have wanted it. This is not a "really serious" proposal, but I wanted to see what other people's comments were about lengthy multiple assignments and how to deal with them. Sometimes I wish I had an alternative way to do assignment. Example:   foo, bar, baz, alpha, beta, gamma, fred, bill, joey = \*values In a case like that, my eye has to scan a long way to the right before finding the equal sign and grasping that this is a multiple assignment. I like this better:   vars = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey]   assign values, vars Note that this wouldn't be a method call (like alias\_method) but a keyword (like alias) unless "binding of caller" was permitted... which is another thing I've wanted but I suppose will never happen. Comments, questions, projectiles? Hal ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [8 July 2013 21:37 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/2 "2013-07-08T21:37:23Z")
At the moment there is no other way I am aware of to introduce local variables \_at runtime\_. While you can do things like eval("foo = 123") the remaining code won't be using the local variable. $ ruby -e 'b=binding;eval("x=10", b);puts x' -e:1:in `\': undefined local variable or method `x' for main:Object (NameError) $ ruby -e 'b=binding;eval("x=10", b);eval("puts x", b)' 10 How about data = {} [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey].each\_with\_index do |s,i|   data[s] = values[i] end puts data[:baz] or even data = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey].each\_with\_index.each\_with\_object {} do |(s,i), d|   d[s] = values[i] end ? Cheers robert > **···** > > On Mon, Jul 8, 2013 at 11:06 PM, Hal Fulton \ wrote: > > > I'm sure this nonexistent feature is not in great demand, but there have > > been different times that I (and other people) have wanted it. > > > > This is not a "really serious" proposal, but I wanted to see what other > > people's comments were about lengthy multiple assignments and > > how to deal with them. > > > > Sometimes I wish I had an alternative way to do assignment. > > > > Example: > > > >   foo, bar, baz, alpha, beta, gamma, fred, bill, joey = \*values > > > > In a case like that, my eye has to scan a long way to the right > > before finding the equal sign and grasping that this is a multiple > > assignment. > > > > I like this better: > > > >   vars = [:foo, :bar, :baz, :alpha, :beta, :gamma, :fred, :bill, :joey] > >   assign values, vars > > > > Note that this wouldn't be a method call (like alias\_method) but > > a keyword (like alias) unless "binding of caller" was permitted... > > which is another thing I've wanted but I suppose will never > > happen. > > > > Comments, questions, projectiles? > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [8 July 2013 23:14 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/3 "2013-07-08T23:14:41Z")
Hal Fulton wrote in post #1114777: > Note that this wouldn't be a method call (like alias\_method) but > a keyword (like alias) unless "binding of caller" was permitted... > which is another thing I've wanted but I suppose will never > happen. > > Comments, questions, projectiles? Yeah, I agree with Robert, there's no need to dynamically create local variables, just use a hash (dynamically created keys are fine). And my initial gut response is: if you're writing that many variables on the left hand side of an assignment, with a single array on the right, there's probably something wrong with the architecture. My other counter-proposal is: hit enter. If the line is too long, develop a syntactic signature for the pattern. For example:     foo, bar, baz, alpha, beta,         gamma, fred, bill, joey = \*values (i.e. lining up the rightmost column, so it's clear that all wrapped lines lead to the single assignment operator). Still not great, but at least the line isn't absurdly long, and you don't have to scan as far to see the '=' Finally, as a bike-shedding nit-pick: if it were a keyword, convention suggests there'd be no comma; and I think putting the destinations on the right is a bit confusing. So if I had to choose, I'd go for:     assign %I[a b c] values But again, that's a big "if", and all in all I'm not too keen on the idea of dynamically creating local variables. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![7stud2](https://avatars.discourse-cdn.com/v4/letter/7/9de053/32.png) [@7stud2](https://rubytalk.org/u/7stud2)\ **Post date:** [9 July 2013 08:08 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/4 "2013-07-09T08:08:11Z")
Once you get to that many local variables I'm sure you could define a class to handle the behaviour you want. Once you start using variables where the names are important, you'd be better of with a Hash. That's the whole point of Hashes. > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Robert\_K1](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/robert_k1/32/1830_2.png) [@Robert\_K1](https://rubytalk.org/u/Robert_K1)\ **Post date:** [9 July 2013 06:45 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/5 "2013-07-09T06:45:50Z")
> Hal Fulton wrote in post #1114777: > \> > \> Note that this wouldn't be a method call (like alias\_method) but > \> a keyword (like alias) unless "binding of caller" was permitted... > \> which is another thing I've wanted but I suppose will never > \> happen. > \> > \> Comments, questions, projectiles? > > Yeah, I agree with Robert, there's no need to dynamically create local > variables, just use a hash (dynamically created keys are fine). And my > initial gut response is: if you're writing that many variables on the > left hand side of an assignment, with a single array on the right, > there's probably something wrong with the architecture. That situation frequently occurs when reading data e.g. from CSV files. If the file has that many columns it makes sense to have local variables for them to ease handling. OTOH then you probably use something like CSV.foreach "a.csv" do |foo, bar, baz, alpha, beta|   puts "foo is #{foo}" end Or one defines a Struct and puts values in there instead of having them in an Array. My other counter-proposal is: hit enter. If the line is too long, > develop a syntactic signature for the pattern. For example: > >     foo, bar, baz, alpha, beta, >         gamma, fred, bill, joey = \*values > > (i.e. lining up the rightmost column, so it's clear that all wrapped > lines lead to the single assignment operator). Still not great, but at > least the line isn't absurdly long, and you don't have to scan as far to > see the '=' I like that approach. > Finally, as a bike-shedding nit-pick: if it were a keyword, convention > suggests there'd be no comma; and I think putting the destinations on > the right is a bit confusing. So if I had to choose, I'd go for: > >     assign %I[a b c] values > > But again, that's a big "if", and all in all I'm not too keen on the > idea of dynamically creating local variables. I forgot to mention: I do not see the original issue as such a big one, so my general bias would be against going through some hoops just to avoid lengthy left hand sides. I don't have them that often and if I have it does not bother me that much. Kind regards robert > **···** > > On Tue, Jul 9, 2013 at 1:14 AM, Matthew Kerwin \ wrote: > > -- > remember.guy do |as, often| as.you\_can - without end > [http://blog.rubybestpractices.com/](http://blog.rubybestpractices.com/) ---
**Author:** ![HAL\_90001](https://yyz1.discourse-cdn.com/flex029/user_avatar/rubytalk.org/hal_90001/32/2046_2.png) [@HAL\_90001](https://rubytalk.org/u/HAL_90001)\ **Post date:** [9 July 2013 14:27 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/6 "2013-07-09T14:27:09Z")
I agree with 95% of the comments people made in this thread. I think the "proper" solution in my situation(s) is to define a class or at least a struct. FWIW, I see this mostly in code that is not my own. I don't usually use length multiple assignment like that (and I \*do\* break up the lines whether I wrote it originally or not). Cheers, Hal > **···** > > On Tue, Jul 9, 2013 at 3:08 AM, Joel Pearson \ wrote: > > > Once you get to that many local variables I'm sure you could define a > > class to handle the behaviour you want. > > Once you start using variables where the names are important, you'd be > > better of with a Hash. That's the whole point of Hashes. > > > > -- > > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Joel\_VanderWerf](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@Joel\_VanderWerf](https://rubytalk.org/u/Joel_VanderWerf)\ **Post date:** [9 July 2013 18:44 UTC](https://rubytalk.org/t/a-very-half-baked-idea-setting-local-variables/68165/7 "2013-07-09T18:44:59Z")
> Hal Fulton wrote in post #1114777: > > > Note that this wouldn't be a method call (like alias\_method) but > > a keyword (like alias) unless "binding of caller" was permitted... > > which is another thing I've wanted but I suppose will never > > happen. ... > My other counter-proposal is: hit enter. If the line is too long, > develop a syntactic signature for the pattern. For example: > >      foo, bar, baz, alpha, beta, >          gamma, fred, bill, joey = \*values Or, taking Matthew's suggestion a bit further:      foo, bar, baz, alpha, beta,          gamma, fred, bill, joey,        = \*values A line beginning with an equals sign is visually conspicuous. > **···** > > On 07/08/2013 04:14 PM, Matthew Kerwin wrote: