# Creating and raising custom exception in Ruby C extension **URL:** \ **Category:** Ruby\ **Created:** [October 22, 2009, 2:31pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712 "2009-10-22T14:31:02Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 2:31pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/1 "2009-10-22T14:31:02Z")
Hi, I’m trying to create a CustomError exception in a Ruby C extension and raise it: VALUE class\_standard\_error = rb\_const\_get(rb\_cObject, rb\_intern(“StandardError”)); VALUE class\_custom\_error = rb\_define\_class\_under(class\_standard\_error, “ClassError”, rb\_cObject); rb\_raise(class\_custom\_error, “Oh, a custom error occurred !!!”); Unfortunatelly when running it I get: ArgumentError: wrong number of arguments(1 for 0) ./test\_unit.rb:22:in `initialize' ./test_unit.rb:22:in`new’ ./test\_unit.rb:22:in `my_function' ./test_unit.rb:22:in`test\_01 Being “my\_function” the Ruby method calling to the above C code. I suspect that the line: rb\_raise(class\_custom\_error, “Oh, a custom error occurred !!!”); is not correct. How should look the first argument? Thanks a lot. ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 2:36pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/2 "2009-10-22T14:36:53Z")
El Jueves, 22 de Octubre de 2009, Iñaki Baz C. escribió: > ArgumentError: wrong number of arguments(1 for 0) > > Thanks a lot. By inspecting the API I’ve realized that first argument must be an instance/object of the class: – rb\_raise(VALUE exception\_object, const char\* format\_string, …) So I must use “rb\_class\_new\_instance”, am I right? ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 2:40pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/3 "2009-10-22T14:40:59Z")
El Jueves, 22 de Octubre de 2009, Iñaki Baz C. escribió: > Hi, I’m trying to create a CustomError exception in a Ruby C extension and > raise it: > > VALUE class\_standard\_error = rb\_const\_get(rb\_cObject, > rb\_intern(“StandardError”)); VALUE class\_custom\_error = > rb\_define\_class\_under(class\_standard\_error, “ClassError”, rb\_cObject); > rb\_raise(class\_custom\_error, “Oh, a custom error occurred !!!”); Ops, this is wrong as ClassError should be a child of StandardError rather than a be under it. ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 2:55pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/4 "2009-10-22T14:55:38Z")
El Jueves, 22 de Octubre de 2009, Iñaki Baz C. escribió: > ArgumentError: wrong number of arguments(1 for 0) > ./test\_unit.rb:22:in `initialize' ./test_unit.rb:22:in`new’ > ./test\_unit.rb:22:in `my_function' ./test_unit.rb:22:in`test\_01 > > Being “my\_function” the Ruby method calling to the above C code. > > I suspect that the line: > rb\_raise(class\_custom\_error, “Oh, a custom error occurred !!!”); > is not correct. How should look the first argument? Let’s try the following real code: VALUE class\_standard\_error = rb\_const\_get(rb\_cObject, rb\_intern(“StandardError”)); VALUE argv[0]; VALUE new\_error = rb\_class\_new\_instance(0, argv, class\_standard\_error); rb\_raise(new\_error, “Oh an error ocurred !!!”); When calling the function containing it from Ruby I get: NoMethodError: undefined method `new’ for #\ What am I doing wrong? Thanks a lot. ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 3:02pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/5 "2009-10-22T15:02:04Z")
On Thu, Oct 22, 2009 at 3:55 PM, Iñaki Baz C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: >     VALUE class\_standard\_error = rb\_const\_get(rb\_cObject, rb\_intern(“StandardError”)); >     VALUE argv[0]; >     VALUE new\_error = rb\_class\_new\_instance(0, argv, class\_standard\_error); >     rb\_raise(new\_error, “Oh an error ocurred !!!”); why not simple: VALUE custom\_error = rb\_define\_class(“CustomError”, rb\_eStandardError); rb\_raise(custom\_error, “An error occured!”); ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 2:59pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/6 "2009-10-22T14:59:43Z")
El Jueves, 22 de Octubre de 2009, Iñaki Baz C. escribió: > > is not correct. How should look the first argument? > > NoMethodError: undefined method `new’ for #\ > > What am I doing wrong? Definitively the line rb\_raise(new\_error, “Oh an error ocurred !!!”); is wrong. I think that “VALUE exception\_object” (as the function requires as first argument) cannot be a class instance. API: rb\_raise(VALUE exception\_object, const char\* format\_string, …) ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 3:11pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/7 "2009-10-22T15:11:26Z")
El Jueves, 22 de Octubre de 2009, Nikolai L. escribió: > On Thu, Oct 22, 2009 at 3:55 PM, Iñaki Baz C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > ``` > > VALUE class_standard_error = rb_const_get(rb_cObject, > > > > ``` > > > > rb\_intern(“StandardError”)); VALUE argv[0]; > > VALUE new\_error = rb\_class\_new\_instance(0, argv, > > class\_standard\_error); rb\_raise(new\_error, “Oh an error ocurred !!!”); > > why not simple: > > VALUE custom\_error = rb\_define\_class(“CustomError”, rb\_eStandardError); > rb\_raise(custom\_error, “An error occured!”); Thanks, I’ve realized right now that first parameter in “rb\_raise” can be “VALUE class”. Let me try 🙂 Really thanks a lot. ---
**Author:** ![ISSSSaki\_Baz\_C](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/51bf81/32.png) [@ISSSSaki\_Baz\_C](https://www.ruby-forum.com/u/ISSSSaki_Baz_C)\ **Post date:** [October 22, 2009, 3:14pm UTC](https://www.ruby-forum.com/t/creating-and-raising-custom-exception-in-ruby-c-extension/177712/8 "2009-10-22T15:14:22Z")
El Jueves, 22 de Octubre de 2009, Iñaki Baz C. escribió: > > rb\_raise(custom\_error, “An error occured!”); > > Thanks, I’ve realized right now that first parameter in “rb\_raise” can be > “VALUE class”. > > Let me try 🙂 > > Really thanks a lot. Done thanks to you: VALUE class\_xdms\_error = rb\_define\_class(“XDMSError”, rb\_eStandardError); VALUE class\_xdms\_url\_parsing\_error = rb\_define\_class(“XDMSURLParsingError”, class\_xdms\_error); rb\_raise(class\_xdms\_url\_parsing\_error, “An error occured!”); 🙂