Rails: Creating new Ruby on Rails app in existing directory

Question

I've been away from Ruby on Rails development for some time, going through several system updates. This occurred on Mac OS X Sierra, with its system version of Ruby (2.0.0p648), and Rails 4.0.2.

Creating a new app (rails new appname) works fine when the appname directory doesn't exist---the command creates the app and populates it as it should. However, despite what all the guidebooks and tutorials say, it fails when such a directory exists (even when it's empty). You also can't create an empty directory, cd into it, and run rails new .

The output of the failed command looks like this:

exist
/Library/Ruby/Gems/2.0.0/gems/railties-4.0.2/lib/rails/generators/app_base.rb:97:in create_root': uninitialized constant Rails::Generators::AppBase::FileUtils (NameError) from (eval):1:in create_root' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/command.rb:27:in run' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/invocation.rb:126:in invoke_command' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/invocation.rb:133:in block in invoke_all' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/invocation.rb:133:in each' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/invocation.rb:133:in map' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/invocation.rb:133:in invoke_all' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/group.rb:232:in dispatch' from /Library/Ruby/Gems/2.0.0/gems/thor-0.20.0/lib/thor/base.rb:466:in start' from /Library/Ruby/Gems/2.0.0/gems/railties-4.0.2/lib/rails/commands/application.rb:43:in <top (required)>' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:68:in require' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:68:in require' from /Library/Ruby/Gems/2.0.0/gems/railties-4.0.2/lib/rails/cli.rb:15:in <top (required)>' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:68:in require' from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:68:in require' from /Library/Ruby/Gems/2.0.0/gems/railties-4.0.2/bin/rails:9:in <top (required)>' from /usr/bin/rails:22:in load' from /usr/bin/rails:22:in `'

How do I get rails to be able to create the app in an existing directory?

Answer 1

For me, I just needed a way of creating a Rails app inside an existing directory.

The directory already had a .git folder inside it, and I also wanted to use the same git repository which the current app was using for the rails app.

Here's how I did it:

All I had to do was to cd into the folder where the app resides:

cd myapp

And then create the rails app inside the folder, skipping git in the process to avoid git conflict and specifying postgresql as my database:

rails new . --database=postgresql --skip-git

Note: The existing project didn't have a .gitignore file, so since my rails new command skipped git, I had to manually create the .gitignore file.

That's all.

I hope this helps

Answer 2

After fruitless online searches for the same problem, I went straight to the reported source: Line 97 of /Library/Ruby/Gems/2.0.0/gems/railties-4.0.2/lib/rails/generators/app_base.rb. That line looks like this:

FileUtils.cd(destination_root) unless options[:pretend]

According to the error message, it can't find FileUtils, treating it as an uninitialized constant. This line is also the only place in the app_base.rb file that uses FileUtils.

I went to the top of the file and added require 'fileutils' to its requirements. I saved it (this required the admin password), and rails new . worked perfectly.

While this fixes the immediate problem, I still have questions. Was this always there, and I haven't noticed, or did it appear after an upgrade as I surmised (most likely from Ruby 1.8 or 1.9 to Ruby 2.0). What changed to cause it?