# Create variables with caller scope **URL:** \ **Category:** ruby-talk\ **Created:** [18 January 2008 11:01 UTC](https://rubytalk.org/t/create-variables-with-caller-scope/43873 "2008-01-18T11:01:40Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Jari\_Williamsson](https://avatars.discourse-cdn.com/v4/letter/j/c4cdca/32.png) [@Jari\_Williamsson](https://rubytalk.org/u/Jari_Williamsson)\ **Post date:** [18 January 2008 11:01 UTC](https://rubytalk.org/t/create-variables-with-caller-scope/43873/1 "2008-01-18T11:01:40Z")
Is it possible for a method to create new variables that becomes in the scope of the caller (instead of the scope of the method)? I guess I mean to get a method to behave much like macros or templates in C/C++. Something like this: > **···** > > --- > def create\_some\_variables(varname1, varname2) >     # Create the variables and initialize with values > end > > create\_some\_variables("a", "b") > # Display the values of those variables > puts a > puts b > --- > > mvh/ >      Jari W. ---
**Author:** ![Jean-Francois\_Tran](https://avatars.discourse-cdn.com/v4/letter/j/c89c15/32.png) [@Jean-Francois\_Tran](https://rubytalk.org/u/Jean-Francois_Tran)\ **Post date:** [18 January 2008 12:15 UTC](https://rubytalk.org/t/create-variables-with-caller-scope/43873/2 "2008-01-18T12:15:17Z")
Jari Williamsson : > Is it possible for a method to create new variables that > becomes in the scope of the caller (instead of the scope > of the method)? I guess I mean to get a method to behave > much like macros or templates in C/C++. Why not using a block ? > Something like this: > --- > def create\_some\_variables(varname1, varname2) >     # Create the variables and initialize with values > end def create\_some\_variables(\*args)   # Create object\_1 and object\_2 and initialize with values   # ...   # pass them to the block   yield object\_1, object\_2 if block\_given? end > create\_some\_variables("a", "b") > # Display the values of those variables > puts a > puts b create\_some\_variables(...) do |a,b|   # Display the values of those variables   puts a   puts b   # do something with a and b   # ... end     -- Jean-François. ---
**Author:** ![Jari\_Williamsson](https://avatars.discourse-cdn.com/v4/letter/j/c4cdca/32.png) [@Jari\_Williamsson](https://rubytalk.org/u/Jari_Williamsson)\ **Post date:** [18 January 2008 12:27 UTC](https://rubytalk.org/t/create-variables-with-caller-scope/43873/3 "2008-01-18T12:27:33Z")
Jean-François Trân wrote: > Jari Williamsson : > > > Is it possible for a method to create new variables that > > becomes in the scope of the caller (instead of the scope > > of the method)? I guess I mean to get a method to behave > > much like macros or templates in C/C++. > > Why not using a block ? Because the created variables will "only" get block scope, if I understand your sample code correctly. And calling the create\_some\_variables() multiple times would create multiple stacked blocks. But giving it a bit more thought, I think I should redesign the code a bit and let the method instead dynamically create a class where all the created variables are stored and then returned an instance of that class. Best regards, Jari Williamsson > **···** > > > > Something like this: > > > --- > > > def create\_some\_variables(varname1, varname2) > > >     # Create the variables and initialize with values > > > end > > > > def create\_some\_variables(\*args) > >   # Create object\_1 and object\_2 and initialize with values > >   # ... > >   # pass them to the block > >   yield object\_1, object\_2 if block\_given? > > end > > > > > create\_some\_variables("a", "b") > > > # Display the values of those variables > > > puts a > > > puts b > > > > create\_some\_variables(...) do |a,b| > >   # Display the values of those variables > >   puts a > >   puts b > > > >   # do something with a and b > >   # ... > > end > > > >     -- Jean-François. ---
**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:** [18 January 2008 12:37 UTC](https://rubytalk.org/t/create-variables-with-caller-scope/43873/4 "2008-01-18T12:37:29Z")
OpenStruct and Hash come to mind. One of those is usually far better than the hack you attempted initially. Btw, there is another issue with this: local variables created dynamically in a scope cannot be used directly (i.e. the same way as if they were defined in the scope directly): $ ruby -e 'def f() eval("x=1", binding); p x end; f' -e:1:in `f': undefined local variable or method `x' for main:Object (NameError)         from -e:1 13:35:55 /cygdrive/c/SCMws/RKlemme/OPSC\_Gold\_bas\_dev\_R1.2\_perf/bas $ ruby -e 'def f() eval("x=1", binding); p(eval("x", binding)) end; f' 1 13:36:27 /cygdrive/c/SCMws/RKlemme/OPSC\_Gold\_bas\_dev\_R1.2\_perf/bas So you need to use some name passing mechanism anyway. And if you do that you can use a Hash immediately which is much easier and clearer. Kind regards robert > **···** > > 2008/1/18, Jari Williamsson \: > > > Jean-François Trân wrote: > > \> Jari Williamsson : > > \>\> Is it possible for a method to create new variables that > > \>\> becomes in the scope of the caller (instead of the scope > > \>\> of the method)? I guess I mean to get a method to behave > > \>\> much like macros or templates in C/C++. > > \> > > \> Why not using a block ? > > > > Because the created variables will "only" get block scope, if I > > understand your sample code correctly. And calling the > > create\_some\_variables() multiple times would create multiple stacked blocks. > > > > But giving it a bit more thought, I think I should redesign the code a > > bit and let the method instead dynamically create a class where all the > > created variables are stored and then returned an instance of that class. > > -- > use.inject do |as, often| as.you\_can - without end