I believe that this is a rails 3.0 bug. In both 3.0 and 3.1 ActiveRecord::Relation's #build is an alias for #new. But somehow, in rails 3.0 this behaviour is not the same, #build will increase the "size counter" and #new will not.
This was probably fixed in rails 3.1. Everton Moreth 2011/9/22 Nicolás Sanguinetti <[email protected]> > On Thu, Sep 22, 2011 at 11:12 AM, Daro <[email protected]> wrote: > > Supose I have a simple has_many relationship betwen model_1 and > > model_2: > > > > class Model1 < ActiveRecord::Base > > has_many :models_2 > > end > > > > class Model2 < ActiveRecord::Base > > belongs_to :model_1 > > end > > > > Now, I create an instance of Model2 through the relationship: > > > > irb>m1 = Model1.first > > irb>m2 = m1.models_2.new > > > > Now, if I want to ask for the size of the relationship, there's a huge > > difference between Rails 3.0.x and Rails 3.1. > > > > Following the previous example, in Rails 3.0.x i get: > > > > irb>m1.models_2.any? > > irb>false > > irb>m1.models_2.size > > irb>0 > > > > This means, new objects are not being considered > > > > This exact same query in Rails 3.1: > > > > irb>m1.models_2.any? > > irb>true #OMG!! > > irb>m1.models_2.size > > irb>1 > > So, the solution is: > > > > irb>m1.models_2.all.any? > > irb>false > > irb>m1.models_2.all.size > > irb>0 > > > > If I have to change ALL my relationships with .all, I'm in a big > > trouble... am I missing something? > > Thank you very much. > > Looking a thttps:// > github.com/rails/rails/blob/v3.1.0/activerecord/lib/active_record/relation.rb#L141-143 > (and the same in v3.0.10, for example) I can't figure out why that > isn't the same, since the code is pretty much the same, so I'm > probably missing something. > > That said, you have 3 ways of querying the size of an ActiveRecord > relation: > > * #length will load all the objects into an array (unless they are > already loaded) and then return the array's size. > * #count will force a DB count and return that result, without loading > the model instances into memory. > * #size will, if the objects are already loaded in an array, return > the #length, or otherwise call #count. > > So you don't need to force an "all", that will load your objects in > memory. Just calling #count should do. > > Cheers, > -foca > > > -- > > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Core" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > [email protected]. > > For more options, visit this group at > http://groups.google.com/group/rubyonrails-core?hl=en. > > > > > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Core" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rubyonrails-core?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-core?hl=en.
