Rails新手：在activerecord中添加条件？

Question

我有一个用于过滤查询的表单。某些表单属性是可选的;我只是想知道如何将它们附加为主动记录条件，如果（且仅当）它们具有设定值时？

其中有相当一部分人，所以我宁愿不对每种潜在价值模式进行单独查询。有什么建议么？

举一个具体的例子：

people = People.paginate(
    :all, 
    :include => [:people_postcodes, :people_specialties, :people_states], 
    :conditions => ["people_specialties.people_type_id = %s AND (people_postcodes.postcode_id = %s OR people_states.state_id = %s)" % [self.people_type_id, postcodeid.id, stateid]], 
    :page => page, 
    :per_page => 16 
) 

我将如何最好的去创造只有在可选的“国籍”属性填充一个额外的条件（说“国籍”）？

Answer 1

首先，你的条件有点不安全。你正在做基本的ruby文本替换，这会让站点用户注入他们想要的任何恶意的sql。相反，格式化如下：

people = People.paginate(
    :all, 
    :include => [:people_postcodes, :people_specialties, :people_states], 
    :conditions => ["people_specialties.people_type_id = ? AND (people_postcodes.postcode_id = ? OR people_states.state_id = ?)", self.people_type_id, postcodeid.id, stateid], 
    :page => page, 
    :per_page => 16 
) 

要回答你的问题，没有自然的方法来处理Rails 2.x中的另一个条件。我会这样做：

conditions = ["people_specialties.people_type_id = ? AND (people_postcodes.postcode_id = ? OR people_states.state_id = ?)", self.people_type_id, postcodeid.id, stateid] 

if params[:nationality] 
    conditions.first += " and nationality = ?" 
    conditions.push params[:nationality] 
end 

people = People.paginate(
    :all, 
    :include => [:people_postcodes, :people_specialties, :people_states], 
    :conditions => conditions, 
    :page => page, 
    :per_page => 16 
) 

在上面的例子中，我假设国籍作为参数传入，但根据需要进行调整。我创建了原始条件数组，然后追加第一个元素（实际条件字符串）并在数组的末尾添加一个元素：国籍值。

我希望这有助于！