我看了很多 RAILS 的例子，都是用 scaffold 创建的。包括到数据库 rake db:migrate rake db:create 之类的，而我则选择通过运行 SQL 代码，或者使用 PHPMYADMIN 来直接创建和维护 MYSQL。
这样可不可以呢，我试过，是可以的。在 RAILS 下，我再手动创建了 models 下的对应 rb 文件，例如我在 phpmyadmin 里面创建了一个 users 表，那么我就在 rails models 下创建一个 user.rb 的文件。
大致内容如下：
class User < ActiveRecord::Base attr_accessible :email, :unn has_many :microposts end
这样是没问题的。
然后我再创建了一个 microposts 表，内容如下：
class Micropost < ActiveRecord::Base attr_accessible :content, :user_uid belongs_to :user end
user 表里有一个 uid 字段，是表示用户的 ID 的。
然后把 user 和 micropost 关联一下 分别是 has_many 和 belongs_to 关系
这个时候，我在 IRB 环境下进行测试：first_user = Users.first，是可以查询到正确的数据的。但是当我 first_user.microposts 这样查询的时候，就出错了，出错内容如下：
NoMethodError: undefined method microposts' for #<Users:0x00000100be24f8>
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/activemodel-3.2.3/lib/active_model/attribute_methods.rb:407:inmethod_missing'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/activerecord-3.2.3/lib/active_record/attribute_methods.rb:148:in method_missing'
from (irb):112
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands/console.rb:47:instart'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in start'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands.rb:41:in'
from /Users/JasonJiang/ror/TestSQL/script/rails:6:in require'
from /Users/JasonJiang/ror/TestSQL/script/rails:6:in'
from -e:1:in load'
from -e:1:in
请教大家一下，这个问题该是怎么回事啊，谢谢！
没有的，显示如下：
irst_user.micropost.content
NoMethodError: undefined method micropost' for #<User:0x00000101c38320>
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/activemodel-3.2.3/lib/active_model/attribute_methods.rb:407:inmethod_missing'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/activerecord-3.2.3/lib/active_record/attribute_methods.rb:148:in method_missing'
from (irb):31
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands/console.rb:47:instart'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in start'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands.rb:41:in'
from /Users/JasonJiang/ror/TestSQL/script/rails:6:in require'
from /Users/JasonJiang/ror/TestSQL/script/rails:6:in'
from -e:1:in load'
from -e:1:in
first_user.micropost.content
NoMethodError: undefined method micropost' for #<User:0x00000101c38320>
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/activemodel-3.2.3/lib/active_model/attribute_methods.rb:407:inmethod_missing'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/activerecord-3.2.3/lib/active_record/attribute_methods.rb:148:in method_missing'
from (irb):31
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands/console.rb:47:instart'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in start'
from /Users/JasonJiang/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.2.3/lib/rails/commands.rb:41:in'
from /Users/JasonJiang/ror/TestSQL/script/rails:6:in require'
from /Users/JasonJiang/ror/TestSQL/script/rails:6:in'
from -e:1:in load'
from -e:1:in
重要的错误提示我觉得应该是这句
first_user.microposts
Micropost Load (0.3ms)ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column SELECT microposts.* FROM microposts WHERE microposts.user_id = 1
'microposts.user_id'Mysql2::Error: Unknown column 'microposts.user_id' in 'where clause': SELECT microposts.* FROM microposts WHERE microposts.user_id = 1
in 'where clause': SELECT microposts.* FROM microposts WHERE microposts.user_id = 1
ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'microposts.user_id' in 'where clause': SELECT microposts.* FROM microposts WHERE microposts.user_id = 1
class User < ActiveRecord::Base attr_accessible :email, :unn
has_many :microposts, :foreign_key => 'user_uid' end