ruby mysql连接错误

我正在使用MySQL和ruby 1.8.6。我想连接到MySQL，因此我正在使用ActiveRecordGem。我的代码是

def initialize

    @db_adapter  = "mysql2"
    @db_host     = "localhost"
    @db_database = "database_name"
    @db_user     = "root"
    @db_password = "root123"
    con = nil

end

def database_connection
           con = ActiveRecord::Base.establish_connection(  
              :adapter  => $db_adapter,  
              :host     => $db_host,  
              :database => $db_database,
              :user     => $db_user,
              :password => $db_password  
           )

           return con
end

但是当我尝试连接时，它给了我这个错误

/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.8/lib/active_record/connection_adapters/abstract/connection_specification.rb:76:in `establish_connection': Please install the  adapter: `gem install activerecord--adapter` (no such file to load -- active_record/connection_adapters/_adapter) (RuntimeError)
    from /cmf/samnew/build/Controller/databaseConnection.rb:32:in `database_connection'
    from controller.rb:23

试一试

---

错误显示未安装

activerecord--adapter

gem。您可以使用以下命令安装gem

gem install activerecord--adapter.

---

运行gem install activerecord adapter并再次尝试说明@instance_变量与$global_变量完全不同。在database_connection函数中打印变量$db_adapter，我认为您需要变量@db_adapter。

gem install activerecord--adapter.