modeling and querry difference?

rubyonrails-talk
1

HI,   I have this type of code where I used a modeling like 'user.profile_photo' from user object I am trying to find profile photo.but it is happened in a loop so just I want to know that how modeling works ? Internally it is a query if so then executing such thing inside a loop is a expensive. so when to use query and when to use modeling any feasible solution for a such a problem.

e.g:- @group=Group.find(group_id)     group_users=@group.users.invitation_accepted     for user in group_users       if !@profile_user.include?(user)         if !user.profile_photo.nil?           @profile_user << user         end       end     end

2

hello,

@users = User.invitation_accepted @users.each { |user| @profile_user << user if (@profile_user.include? (user) and user.profile_photo.nil?) }

in your model:

named_scope :grouped, lambda { |id| { :include => :groups, :conditions => "groups.id = #{id} and groups.user_id = user.id" } }

def invitation_accepted    User.grouped.find .... end

untested

3

what is named_scope and how it is useful in a performance perspective?

4

named_scope is a smart way to chain model find options with synonyms but here it isn't responsible for the query optimization

look at :include it iniate a join with group so your 2 queries are reduced to one query look at your development.log to see, what activerecord is building for you and if your query looks good

hint: look for some basic active records tutorial, espacially for eager loading and lazy loading

best regards