The Ruby NameError Uninitialized Constant Error

The open-source programming language Ruby is known for its clear syntax and ease of use. That doesnt mean you wont occasionally run into an error message. One of the most vexing is the NameError Uninitialized Constant exception because it has more than one cause. The syntax of the exception follows this format: NameError: uninitialized constant Something or NameError: uninitialized constant Object::Something (where various class names are in place of Something) Ruby NameError Uninitialized Constant Causes The Uninitialized Constant error is a variation of a regular NameError exception class. It has several possible causes.   Youll see this error when the code refers to a class or module that it cant find, often because the code doesnt include require, which instructs the Ruby file to load the class.In Ruby, variables/methods begin with lowercase letters, while classes begin with uppercase letters. If the code doesnt reflect this distinction, youll receive the Uninitialized Constant exception.Still another possible cause for the  NameError  error is that youve made a simple typo in the code.  Ruby is case sensitive, so TestCode and Testcode are completely different.  The code contains mention of rubygems, which is deprecated in all but old versions of Ruby. How to Fix the Error To troubleshoot your code, examine it for the possible causes listed above one at a time. If you find a problem, address it. For example, go through the code looking for a discrepancy in uppercase and lowercase usage on variables and classes.  If you find one and correct it, your problem is probably solved. If it isnt, continue through the other possible causes, fixing as you go. If the class you refer to in the code is in another module, refer to it with its full name like this: #!/usr/bin/env rubymodule MyModule class MyClass; endendc MyModule::MyClass.new About Ruby Exceptions Exceptions are how Ruby draws your attention to problems in the code. When an error in the code is encountered, an  exception is raised or thrown and the program shuts down by default. Ruby publishes an exception hierarchy with predefined classes. NameErrors are in the StandardError class, along with RuntimeError, ThreadError, RangeError, ArgumentError and others. This class includes most of the normal exceptions that you encounter in typical Ruby programs.