ActiveRecord.find方法中":conditions"的应用

在SQL文的查询条件中经常会用得到关键字in，例如：

SELECT * FROM accounts WHERE nick_name = 'nicknm' AND id IN ("1","2");

 

此时如果利用Rails的find方法，代码如下所示：

 

 

require "rubygems"
require "active_record"

module ActiveRecord
class Base
def self.each_cons(n)
offset = 0
loop do
size = yield(offset)
break if size < n
offset += n
end
end
end
end



ActiveRecord::Base.establish_connection(
:adapter => 'mysql',
:host => 'localhost',
:database => 'myapp_development',
:username => 'my',
:password => '123'
)

class Account < ActiveRecord::Base
establish_connection(
:adapter => 'mysql',
:host => 'localhost',
:database => 'myauth_development',
:username => 'my',
:password => '123'
)
end

#condns 是个数组
condns = []
condns << "1"
condns << "2"

#非常值得注意的是：此时传给in(即第二个？)的参数一定要是数组类型的，
#否则返回的不是想要的结果。
#举例说明：如果将condns设置成字符串类型→"1,2"，那么下述find方法解析完的
#SQL是SELECT * FROM accounts WHERE nick_name = 'nicknm' AND id #IN ("1,2");
#而我们期待的结果应该是：
#SELECT * FROM accounts WHERE nick_name = 'nicknm' AND id IN 
#("1","2");
accounts = Account.find(:all, 
:conditions => ["nick_name = ? and id in (?)",  "nicknm",  condns],
:order => 'id asc',
:limit => 1000)