Undefined method fetch for false:FalseClass

Question

I create a simple rails application and when I run rails s. It emits this stack of errors :-s I tried to reinstall activerecord but it couldn't solve the problem. Moreover, I tried to used rvm to remove all the gemset and reinstall but it's still the same.

/usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:33:in `resolve_string_connection': undefined method `fetch' for false:FalseClass (NoMethodError)
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:23:in `spec'
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/connection_adapters/abstract/connection_specification.rb:127:in `establish_connection'
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/railtie.rb:76:in `block (2 levels) in <class:Railtie>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:26:in `block in on_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:25:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/lazy_load_hooks.rb:25:in `on_load'
from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.2.3/lib/active_record/railtie.rb:74:in `block in <class:Railtie>'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:30:in `instance_exec'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:30:in `run'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:55:in `block in run_initializers'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:54:in `each'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/initializable.rb:54:in `run_initializers'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/application.rb:136:in `initialize!'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/railtie/configurable.rb:30:in `method_missing'
from /home/vic4ever/crowdvn/crowd.vn/config/environment.rb:5:in `<top (required)>'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:251:in `require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:251:in `block in require'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:236:in `load_dependency'
from /usr/local/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:251:in `require'
from /home/vic4ever/crowdvn/crowd.vn/config.ru:4:in `block in <main>'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:51:in `instance_eval'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:51:in `initialize'
from /home/vic4ever/crowdvn/crowd.vn/config.ru:1:in `new'
from /home/vic4ever/crowdvn/crowd.vn/config.ru:1:in `<main>'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:40:in `eval'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/builder.rb:40:in `parse_file'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/server.rb:200:in `app'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/server.rb:46:in `app'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/server.rb:301:in `wrapped_app'
from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.4.1/lib/rack/server.rb:252:in `start'
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/server.rb:70:in `start'
    from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:55:in `block in <top (required)>'
    from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:50:in `tap'
    from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:50:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

Answer 1

You need a databse adapter (i.e., config/database.yml).

I will assume you're using Git for source control for your own safety. It will also help you see the changes that you've made when you follow the directions below.

Generate a new database.yml:

$ cd ~/path/to/my-existing-rails-app
$ rails new my-existing-rails-app --database=sqlite

A series of prompts will ask you if you want to create/overwrite existing files. Keep answering "NO" to the prompts until there you see one that asks to create config/database.yml. Answer "YES" if you see the prompt and continue answering "NO" to the rest.

Instead of --database=sqlite, you can also use --database=postgresql or --database=mysql if you've installed those in your local/development environment.

Even further, there are more options for --database=DATABASE

mysql
oracle
postgresql
sqlite3
frontbase
ibm_db
sqlserver
jdbcmysql
jdbcsqlite3
jdbcpostgresql
jdbc