# Setting global variables in embedded ironruby interpreter **URL:** \ **Category:** IronRuby\ **Created:** [February 9, 2009, 12:38pm UTC](https://www.ruby-forum.com/t/setting-global-variables-in-embedded-ironruby-interpreter/159849 "2009-02-09T12:38:54Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Meinrad\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ecae2f/32.png) [@Meinrad\_R](https://www.ruby-forum.com/u/Meinrad_R)\ **Post date:** [February 9, 2009, 12:38pm UTC](https://www.ruby-forum.com/t/setting-global-variables-in-embedded-ironruby-interpreter/159849/1 "2009-02-09T12:38:54Z")
Hello, I am very pleased that I got everything working and found iron ruby in a quite usable state for me. Congratulations. Question: How do you set a global variable from C#? I found a workaround via setting a local variable scope.SetVariable(“a”, obj) in the scope and assigning it to a global via engine.Execute("$a=a", scope). The Runtime.Globals.GetVariable and SetVariable don’t seem to get / set the ruby globals. Please clarify. BTW: as for local variables: scope.GetVariableNames() does return an empty list. Again a workaround is Execute(“local\_variables”, scope). – henon ---
**Author:** ![Meinrad\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ecae2f/32.png) [@Meinrad\_R](https://www.ruby-forum.com/u/Meinrad_R)\ **Post date:** [February 9, 2009, 1:24pm UTC](https://www.ruby-forum.com/t/setting-global-variables-in-embedded-ironruby-interpreter/159849/2 "2009-02-09T13:24:56Z")
On Mon, Feb 9, 2009 at 12:12 PM, Meinrad R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote: > Oh, i just found out that ScriptScope.GetVariable is throwing an exception … * * * ArgumentNullException: “Value cannot be null. Parameter name: field” ---
**Author:** ![Meinrad\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ecae2f/32.png) [@Meinrad\_R](https://www.ruby-forum.com/u/Meinrad_R)\ **Post date:** [February 9, 2009, 3:42pm UTC](https://www.ruby-forum.com/t/setting-global-variables-in-embedded-ironruby-interpreter/159849/3 "2009-02-09T15:42:52Z")
On Mon, Feb 9, 2009 at 1:05 PM, Meinrad R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote: > > assigning it to a global via engine.Execute(“$a=a”, scope). > > Parameter name: field" > > * * * > > Microsoft.Scripting.Utils.ContractUtils.RequiresNotNull(Object value, > String paramName) > Microsoft.Scripting.SymbolTable.StringToId(String field) > Microsoft.Scripting.Hosting.ScriptScope.GetVariable(String name) sorry forgot to say, that I made sure, that the “name” parameter is _not_ null. I am not yet deep enough into the sources to fix things like these myself. – henon ---
**Author:** ![Meinrad\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ecae2f/32.png) [@Meinrad\_R](https://www.ruby-forum.com/u/Meinrad_R)\ **Post date:** [February 9, 2009, 3:54pm UTC](https://www.ruby-forum.com/t/setting-global-variables-in-embedded-ironruby-interpreter/159849/4 "2009-02-09T15:54:05Z")
On Mon, Feb 9, 2009 at 1:11 PM, Meinrad R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote: > > > > > sorry forgot to say, that I made sure, that the “name” parameter is _not_ > null. > I am not yet deep enough into the sources to fix things like these myself. > > – henon ok, I was too fast on this one. actually it was null because a ruby\_string casted to c# string is null. It is pretty dangerous to assume a value presented as “a” by the debugger to be a System.String when that value comes out from ruby 😉 so the problem is not the exception but rather that GetVariable(“a”) does not find existing local variables which can be evaluated by Execute(“a”). This time I made sure I made no mistake. ---
**Author:** ![Meinrad\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ecae2f/32.png) [@Meinrad\_R](https://www.ruby-forum.com/u/Meinrad_R)\ **Post date:** [February 9, 2009, 7:09pm UTC](https://www.ruby-forum.com/t/setting-global-variables-in-embedded-ironruby-interpreter/159849/5 "2009-02-09T19:09:37Z")
You can find many hosting examples in HostingTests.cs. As for global and top-level local variables: - ``` Variables in ScriptRuntimeRuntime.Globals are mapped to ``` global constants (ie. constants on Object). - ``` Variables in local ScriptScope are not mapped to Ruby ``` top-level local variables. They are looked up via method\_missing on a top-level singleton object. Ruby top-level program executes in a context where “self” is a singleton of Object. IronRuby defines method\_missing on this singleton. If a method name ends with “=” it writes to the scope, otherwise it reads from the scope. ScriptScope scope = Engine.CreateScope(); scope.SetVariable(“x”, 1); scope.SetVariable(“y”, 2); Engine.Execute(“self.z = x + y”, scope); int result = scope.GetVariable(“result”); Assert(result == 3); Ruby global variables don’t have any mapping to DLR scopes. We don’t have any well designed API for them yet, you can do this for now: Ruby.GetExecutionContext(Engine).DefineGlobalVariable(“foo”, 123); Tomas From: removed\_email\_address@domain.invalid [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf Of Meinrad Recheis Sent: Monday, February 09, 2009 3:13 AM To: ironruby-core Subject: [Ironruby-core] setting global variables in embedded ironruby interpreter Hello, I am very pleased that I got everything working and found iron ruby in a quite usable state for me. Congratulations. Question: How do you set a global variable from C#? I found a workaround via setting a local variable scope.SetVariable(“a”, obj) in the scope and assigning it to a global via engine.Execute(“$a=a”, scope). The Runtime.Globals.GetVariable and SetVariable don’t seem to get / set the ruby globals. Please clarify. BTW: as for local variables: scope.GetVariableNames() does return an empty list. Again a workaround is Execute(“local\_variables”, scope). – henon