ActiveRecord::AdapterNotSpecified database configuration does not specify adapter

问题:

When I use heroku open my web app works fine but when I'm using rails s (localhost) I am running into this error:

ActiveRecord::AdapterNotSpecified database configuration does not specify adapter 

Why is this?

This is my database.yml

# PostgreSQL. Versions 8.2 and up are supported. # # Install the pg driver: #   gem install pg # On OS X with Homebrew: #   gem install pg -- --with-pg-config=/usr/local/bin/pg_config # On OS X with MacPorts: #   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config # On Windows: #   gem install pg #       Choose the win32 build. #       Install PostgreSQL and put its /bin directory on your path. # # Configure Using Gemfile # gem 'pg' # default: &default   adapter: postgresql   encoding: unicode   # For details on connection pooling, see rails configuration guide   # http://guides.rubyonrails.org/configuring.html#database-pooling   pool: 5 

And this is my gemfile:

source 'https://rubygems.org'   gem 'pg'  gem 'bootstrap-sass', '~> 3.1.1'  # Bundle edge Rails instead: gem 'rails', github: 'rails/rails' gem 'rails', '4.0.3'  # Use SCSS for stylesheets gem 'sass-rails', '~> 4.0.0'  # Use Uglifier as compressor for JavaScript assets gem 'uglifier', '>= 1.3.0'  # Use CoffeeScript for .js.coffee assets and views gem 'coffee-rails', '~> 4.0.0'  # See https://github.com/sstephenson/execjs#readme for more supported runtimes # gem 'therubyracer', platforms: :ruby  # Use jquery as the JavaScript library gem 'jquery-rails'  # Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks gem 'turbolinks'  # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder gem 'jbuilder', '~> 1.2'  group :doc do   # bundle exec rake doc:rails generates the API under doc/api.   gem 'sdoc', require: false end  group :production do   gem 'rails_12factor', '0.0.2' end  # Use ActiveModel has_secure_password # gem 'bcrypt-ruby', '~> 3.1.2'  # Use unicorn as the app server # gem 'unicorn'  # Use Capistrano for deployment # gem 'capistrano', group: :development  # Use debugger # gem 'debugger', group: [:development, :test] 

回答1:

For you app to work locally you need to:

1. Install Postgresql on your machine
2. Create a database for your development needs (let's call it my_app_development)

3. Change your database.yml to:

   default: &default   adapter: postgresql   encoding: unicode   # For details on connection pooling, see rails configuration guide   # http://guides.rubyonrails.org/configuring.html#database-pooling   pool: 5  development:   

4. run rake db:migrate

回答2:

Your database.yml should look something like this:

default: &default   adapter: postgresql   encoding: unicode   # For details on connection pooling, see rails configuration guide   # http://guides.rubyonrails.org/configuring.html#database-pooling   pool: 5   username: my_username   password: my_password  development:   

Edit development_database_name to your local database name. Also edit my_username and my_password to your correct db username and password.

回答3:

Delete tabs nothing more, ident perfect, such as:

# PostgreSQL. Versions 8.2 and up are supported. # # Install the pg driver: #   gem install pg # On OS X with Homebrew: #   gem install pg -- --with-pg-config=/usr/local/bin/pg_config # On OS X with MacPorts: #   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config # On Windows: #   gem install pg #       Choose the win32 build. #       Install PostgreSQL and put its /bin directory on your path. # # Configure Using Gemfile # gem 'pg' # default: &default   adapter: postgresql   encoding: utf8   pool: 5   host: 192.168.0.121   username: postgres   password: passpostgres  development:    # production:    

回答4:

You didn't show the command causing this query, but this could happen if you pass a string and not a symbol.

For example:

irb(main):001:0> ActiveRecord::Base.establish_connection("#{Rails.env}") ActiveRecord::AdapterNotSpecified: database configuration does not specify adapter 

But then if you use a symbol, it will work.

irb(main):001:0> ActiveRecord::Base.establish_connection("#{Rails.env}".to_sym) => #<:connectionadapters::connectionpool:0x007f2f484a32a0>

回答5:

Why are you using a yml node reference in your database.yml?

You should have something like this:

#config/database.yml development:   adapter: mysql2   encoding: utf8   database: ****   pool: 5   username: ****   password: ****   host: ***.***.***.*** #-> only for third party db server  production:   adapter: postgresql   encoding: utf8   database: ****   pool: 5   username: ****   password: ****   host: ***.***.***.*** #-> only for third party db server 

---

Update

Rails runs using a database. You have to connect to a db to make it work, and to do that you have to define the different connection details in database.yml

To define the right information, you need to appreciate that Rails operates in several environments - development & production being the two most used

To get Rails working in your local (development) environment, you need to define the correct db details. This means you need a database to connect to - which is typically done setting up a local mysql / pgsql server

Bottom line is you connect to a db using:

• hostname
• username
• password
• db name

You need to define these in your config/database.yml file

If you have a server running in your local environment, your database.yml file will look like this:

#config/database.yml development:   adapter: mysql2   encoding: utf8   database: db_name   pool: 5   username: username   password: password 

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