uninitialized constant ActiveRecord

[wikimisu]

各位大大，我是使用"Ruby on Rails網路應用程式開發與建置"的書籍來當作範例....
但是在建立資料庫的時候發生了一些問題，
在lib\tasks\db_setup.rake有下列程式:

env = ENV['RAILS_ENV'] || 'development'
database = "LunchBooks_#{env}"
user = "lunchuser_#{env[0..0]}"

def connect
ActiveRecord::Base.establish_connection(
:adapter => 'mysql',
:host => 'localhost',
:username => 'root',
:password => '1234',
:database => 'mysql'
)
end

task :db_setup do
ActiveRecord::Schema.define do
connect
begin
create_database database
rescue
end
execute "create user #{user}@localhost identified by 'ror'"
execute "grant all privileges on #{database}.* to
'#{user}'@'localhost'"
end

end

task :db_clean do
ActiveRecord::Schema.define do
connect
begin
execute "drop user '#{user}'@'localhost'"
rescue
end
drop_database database
end

end

接著下指令...

> rake environment RAILS_ENV=production db_setup

-- execute("create user lunchuser_p@localhost identified by 'ror'")
-> 0.3590s
-- execute("grant all privileges on LunchBooks_production.* to
'lunchuser_p'@'localhost'")
-> 0.0320s

也都可以執行…
可是再來我又打了

> rake db_setup

rake aborted!
uninitialized constant ActiveRecord

(See full trace by running task with --trace)



我也看過先前網友的意見，加上了 :environment，
但是還是不能執行，請問該如何解決呢??
謝謝!!