# Undefined method error **URL:** \ **Category:** Ruby\ **Created:** [May 19, 2006, 4:26pm UTC](https://www.ruby-forum.com/t/undefined-method-error/61041 "2006-05-19T16:26:27Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![pkspence](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/a88e57/32.png) [@pkspence](https://www.ruby-forum.com/u/pkspence)\ **Post date:** [May 19, 2006, 4:26pm UTC](https://www.ruby-forum.com/t/undefined-method-error/61041/1 "2006-05-19T16:26:27Z")
Still trying to get my head wrapped around the concepts regarding Modules, Classes and their methods. Once an instance of the MyErrorLogger::ErrorLogger class has been instanciated, shouldn’t Komodo be displaying the intellisense for the object? Using the example below, when I type “errorLogger.”, why isn’t a list of the properties and methods of the object displayed? Back on topic, consider the following… #-- myErrorLogger.rb module MyErrorLogger class ErrorLogger ``` def initialize() puts "Instance of MyErrorLogger::ErrorLogger has been created" end def ErrorLogger.PostError(ex) puts "Exception error message: " + ex.to_s end ``` end # class ErrorLogger end # module MyErrorLogger #-- testErrorLogger.rb require ‘myErrorLogger’ include MyErrorLogger def testBed #-- message is displayed in console window as expected errorLogger = MyErrorLogger::ErrorLogger.new #-- “undefined method ‘PostError’” error gets thrown on this line errorLogger.PostError(Exception.new(“test error message”)) end #-- fire it up testBed ---
**Author:** ![pkspence](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/a88e57/32.png) [@pkspence](https://www.ruby-forum.com/u/pkspence)\ **Post date:** [May 19, 2006, 4:59pm UTC](https://www.ruby-forum.com/t/undefined-method-error/61041/2 "2006-05-19T16:59:14Z")
2006/5/19, Patrick S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > #-- myErrorLogger.rb > end > def testBed > > #-- message is displayed in console window as expected > errorLogger = MyErrorLogger::ErrorLogger.new > > #-- “undefined method ‘PostError’” error gets thrown on this line > errorLogger.PostError(Exception.new(“test error message”)) PostError is a method of MyErrorLogger::ErrorLogger, i.e. of the class instance. errorLogger is an instance of MyErrorLogger::ErrorLogger so it cannot know this method. Kind regards robert ---
**Author:** ![pkspence](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/a88e57/32.png) [@pkspence](https://www.ruby-forum.com/u/pkspence)\ **Post date:** [May 19, 2006, 6:22pm UTC](https://www.ruby-forum.com/t/undefined-method-error/61041/3 "2006-05-19T18:22:35Z")
Robert K. wrote: > PostError is a method of MyErrorLogger::ErrorLogger, i.e. of the class > instance. errorLogger is an instance of MyErrorLogger::ErrorLogger so > it cannot know this method. > > Kind regards > > robert I understood that when an instance of a Method::Class has been created, the resulting object would inherit all the methods and properties it was based on. Now I’m confused! ---
**Author:** ![pkspence](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/a88e57/32.png) [@pkspence](https://www.ruby-forum.com/u/pkspence)\ **Post date:** [May 19, 2006, 6:38pm UTC](https://www.ruby-forum.com/t/undefined-method-error/61041/4 "2006-05-19T18:38:56Z")
2006/5/19, Patrick S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > the resulting object would inherit all the methods and properties it was > based on. Now I’m confused! It seems so. What is a “Method::Class” in your terminology? Ok, I try again. All classes are objects but not all objects are classes. A class defines instance methods. These methods can be used in instances of the class and instances of sub classes. Every object can also have singleton methods (there are other names for them as well but I’ll stick with the convention Matz has founded); singleton methods are present in that single instance only, there is no inheritance associated with them whatsoever but you can find them in the singleton class (every object has one and the singleton class has only one instance). Since a class is an object it can have singleton methods. These do roughly the same as static methods in Java, i.e. the operate on the class level. Some code: irb(main):001:0\> class Foo irb(main):002:1\> def bar() # instance method irb(main):003:2\> “bar” irb(main):004:2\> end irb(main):005:1\> end =\> nil irb(main):006:0\> Foo.new.bar =\> “bar” irb(main):007:0\> Foo.bar NoMethodError: undefined method `bar' for Foo:Class from (irb):7 from :0 irb(main):008:0> f=Foo.new => # irb(main):009:0> f.bar => "bar" irb(main):010:0> def f.special() # singleton method irb(main):011:1> "buh!" irb(main):012:1> end => nil irb(main):013:0> f.special => "buh!" irb(main):014:0> Foo.new.special NoMethodError: undefined method `special’ for #Foo:0x3b5b38 from (irb):14 from :0 irb(main):015:0\> def Foo.nana() # singleton method irb(main):016:1\> “nana” irb(main):017:1\> end =\> nil irb(main):018:0\> Foo.nana =\> “nana” irb(main):019:0\> Foo.new.nana NoMethodError: undefined method `nana’ for #Foo:0x3a8ff8 from (irb):19 from :0 Hope it helps… robert ---
**Author:** ![pkspence](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/a88e57/32.png) [@pkspence](https://www.ruby-forum.com/u/pkspence)\ **Post date:** [May 19, 2006, 7:08pm UTC](https://www.ruby-forum.com/t/undefined-method-error/61041/5 "2006-05-19T19:08:38Z")
Robert K. wrote: > 2006/5/19, Patrick S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > > > the resulting object would inherit all the methods and properties it was > > based on. Now I’m confused! > > It seems so. What is a “Method::Class” in your terminology? Oops, I meant “Module::Class”. As for your reply, thanks! I need some time to digest it.