Error "uninitialized constant AWS (NameError)"

If you are receiving this error and you have the "aws-sdk" gem installed, you likely have upgraded to version 2 of the aws-sdk gem unintentionally. Version 2 uses the Aws namespace, not AWS. This allows version 1 and version 2 to be used in the same application.

See this blog post for more information.

You need to install/use the -v1 version of aws-sdk. Simply doing gem 'aws-sdk' or require 'aws-sdk' may use the 2.x version of aws-sdk instead.

To avoid any confusion, for scripts that require 1.x, use:

require 'aws-sdk-v1' # not 'aws-sdk'

And for scripts that require 2.x, use:

gem 'aws-sdk', '~> 2'

as the GitHub documentation indicates.

You might getting this error, because you didn't define the correct aws sdk version in your Gemfile. This can happen while re-bundling old apps with version 1 or 2 installed.

Make sure which version you want to install:

aws-sdk version 3

gem 'aws-sdk', '~> 3'# call sdk    Aws.<whatever>

aws-sdk version 2

gem 'aws-sdk', '~> 2'# call sdk    Aws.<whatever>

aws-sdk version 1

# version constraintgem 'aws-sdk', '< 2'# or # use the v1 gemgem 'aws-sdk-v1'# call sdk    AWS.<whatever>

v1 is scoped under AWS and v2 and v3 scoped under Aws => That allows you to run v1 and v2 side by side.