高效過濾多對多

Question

在我寫的應用程序中，我有可能屬於任何組數的用戶。通過相應的group_membership模型存在has_many關係。

我正在使用報告界面，並希望按組進行過濾，因此我想返回屬於所有列出組的用戶（即使他們屬於其他附加組）。

目前，我反覆根據用戶的成員資格向每個組依次過濾一組用戶，以便在用戶不是當前組的成員時過濾掉用戶。

@users = @account.users.joins(:groups).where("groups.id in (?)",all_groups).pluck('users.id') #All user IDs 
    positions_users = @account.users.joins(:groups).where("groups.id in (?)",positions).pluck('users.id') unless positions.empty? 
    departments_users = @account.users.joins(:groups).where("groups.id in (?)",departments).pluck('users.id') unless departments.empty?  
    locations_users = @account.users.joins(:groups).where("groups.id in (?)",locations).pluck('users.id') unless locations.empty?  
    miscellaneous_users = @account.users.joins(:groups).where("groups.id in (?)",miscellaneous).pluck('users.id') unless miscellaneous.empty? 


    @users = @users.select {|x| positions_users.include? x } unless positions_users.nil? || positions_users.empty? 
    @users = @users.select {|x| departments_users.include? x } unless departments_users.nil? || departments_users.empty? 
    @users = @users.select {|x| locations_users.include? x } unless locations_users.nil? || locations_users.empty? 
    @users = @users.select {|x| miscellaneous_users.include? x } unless miscellaneous_users.nil? || miscellaneous_users.empty? 

有沒有更有效的方法呢？

Answer 1

假設你有一個連接模型UserGroup，您可以添加以下範圍：

class UserGroup 
    scope :group_filter, lambda{|*groups| 
    group_ids = groups.flatten.compact.uniq 
    return self if group_ids.blank? 
    where(:group_id => group_ids) 
    } 
end 

現在你可以這樣做：

filter = UserGroup.group_filter(positions, departments, locations, miscellaneous) 
@users = @account.users.joins(:user_groups).merge(filter) 

和你做！