Mysql Rails：在模型中指定不同的数据库

我正在尝试将Rails（v3.2.2）设置为使用多个数据库。我是基于这个来做这件事的

我的模型：

class Category < ActiveRecord::Base                                                                                                                                                                                                                                                                                                
  establish_connection :category_database                                                                                                                                                                                                                                                                                                                       
  self.primary_key = "cat_id"                                                                                                                                                   

  validates_presence_of :name, :display_name, :description, :icon, :image, :parent_category_id, :create_time                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
end

运行此规范文件时：

require 'spec_helper'                                                                                                                                                           

describe Category do                                                                                                                                                            
  puts "ENV: #{Rails.env}"                                                                                                                                                      
  it { should validate_presence_of :name }                                                                                                                                      
  it { should validate_presence_of :display_name }                                                                                                                              
  it { should validate_presence_of :description }                                                                                                                               
  it { should validate_presence_of :icon }                                                                                                                                      
  it { should validate_presence_of :image }                                                                                                                                     
  it { should validate_presence_of :parent_category_id }                                                                                                                        
  it { should validate_presence_of :create_time }                                                                                                                               

end            

像这样：

>rspec /path/to/category_spec.rb  

  establish_connection(                                                                                                                                                         
    :adapter => "mysql2",                                                                                                                                                       
    :encoding => "utf8",                                                                                                                                                        
    :reconnect => false,                                                                                                                                                      
    :database => "main_cat",                                                                                                                                                 
    :pool => 5,                                                                                                                                                                 
    :username => "root",                                                                                                                                                        
    :password => "blah",                                                                                                                                                            
    :socket => "/var/run/mysqld/mysqld.sock")

test:                                                                                                                                                                           
  adapter: mysql2                                                                                                                                                               
  encoding: utf8                                                                                                                                                                
  reconnect: false                                                                                                                                                              
  database: main_cat                                                                                                                                                         
  pool: 5                                                                                                                                                                       
  username: root                                                                                                                                                                
  password: blah                                                                                                                                                                    
  socket: /var/run/mysqld/mysqld.sock   

我得到：

/home/user/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract/connection_specification.rb:45:in `resolve_hash_connection': database configuration does not specify adapter (ActiveRecord::AdapterNotSpecified)

我还尝试过如下设置建立\u连接：

>rspec /path/to/category_spec.rb  

  establish_connection(                                                                                                                                                         
    :adapter => "mysql2",                                                                                                                                                       
    :encoding => "utf8",                                                                                                                                                        
    :reconnect => false,                                                                                                                                                      
    :database => "main_cat",                                                                                                                                                 
    :pool => 5,                                                                                                                                                                 
    :username => "root",                                                                                                                                                        
    :password => "blah",                                                                                                                                                            
    :socket => "/var/run/mysqld/mysqld.sock")

test:                                                                                                                                                                           
  adapter: mysql2                                                                                                                                                               
  encoding: utf8                                                                                                                                                                
  reconnect: false                                                                                                                                                              
  database: main_cat                                                                                                                                                         
  pool: 5                                                                                                                                                                       
  username: root                                                                                                                                                                
  password: blah                                                                                                                                                                    
  socket: /var/run/mysqld/mysqld.sock   

这会导致相同的异常。（未指定适配器）

奇怪的是，如果我完全放弃建立_连接，并通过database.yml文件应用完全相同的连接配置，如下所示：

>rspec /path/to/category_spec.rb  

  establish_connection(                                                                                                                                                         
    :adapter => "mysql2",                                                                                                                                                       
    :encoding => "utf8",                                                                                                                                                        
    :reconnect => false,                                                                                                                                                      
    :database => "main_cat",                                                                                                                                                 
    :pool => 5,                                                                                                                                                                 
    :username => "root",                                                                                                                                                        
    :password => "blah",                                                                                                                                                            
    :socket => "/var/run/mysqld/mysqld.sock")

test:                                                                                                                                                                           
  adapter: mysql2                                                                                                                                                               
  encoding: utf8                                                                                                                                                                
  reconnect: false                                                                                                                                                              
  database: main_cat                                                                                                                                                         
  pool: 5                                                                                                                                                                       
  username: root                                                                                                                                                                
  password: blah                                                                                                                                                                    
  socket: /var/run/mysqld/mysqld.sock   

它起作用了

Rails似乎完全忽略了建立连接……我是否缺少一些应用程序级别的配置设置或其他什么？如何让Rails识别并建立连接，以便在不同的数据库中放置不同的模型

---

非常感谢

因此，Rails需要默认配置。在这种情况下，database.yml文件仍然需要一个测试数据库。否则，Rails将抛出异常，因为它希望在初始化模型之前建立一些连接。加载默认配置后，Rails稍后将继续初始化模型，然后可以通过建立连接进行模型级数据库配置

我希望这能帮助其他人。我花了相当长的时间运行调试程序

activerecord-3.2.2/lib/active\u record/connection\u adapters/abstract/connection\u specification.rb

---

为了弄明白这一点。

出于几乎相同的原因，我遇到了相同的错误，但我确实做了一个测试：在我的数据库中配置.yml；但问题在于我在模型定义中设置了“建立连接”方法：

  establish_connection 'cm_inv_mgmt_' + Rails.env.downcase

虽然我为生产/登台和开发环境提供了database.yml的部分，但我缺少了cm_inv_mgmt_测试