Method: ActiveRecord::ConnectionHandling#establish_connection

Defined in:

lib/active_record/connection_handling.rb

#establish_connection(spec = ENV["DATABASE_URL"]) ⇒ Object

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, Postgresql, etc):

ActiveRecord::Base.establish_connection(
  adapter:  "mysql",
  host:     "localhost",
  username: "myuser",
  password: "mypass",
  database: "somedatabase"
)

Example for SQLite database:

ActiveRecord::Base.establish_connection(
  adapter:  "sqlite",
  database: "path/to/dbfile"
)

Also accepts keys as strings (for parsing from YAML for example):

ActiveRecord::Base.establish_connection(
  "adapter"  => "sqlite",
  "database" => "path/to/dbfile"
)

Or a URL:

ActiveRecord::Base.establish_connection(
  "postgres://myuser:mypass@localhost/somedatabase"
)

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.

# File 'lib/active_record/connection_handling.rb', line 37

def establish_connection(spec = ENV["DATABASE_URL"])
  resolver = ConnectionAdapters::ConnectionSpecification::Resolver.new spec, configurations
  spec = resolver.spec

  unless respond_to?(spec.adapter_method)
    raise AdapterNotFound, "database configuration specifies nonexistent #{spec.config[:adapter]} adapter"
  end

  remove_connection
  connection_handler.establish_connection self, spec
end