Mongoid finders not working?

问题:

I have set up a rails3+mongoid application and when I open the rails console, none of the finders seem to work - http://d.pr/FNzC

User.all
User.find(:all, :conditions => { first_name => "John" })

both return:

#<Mongoid::Criteria
  selector: {},
  options:  {}>

Am I doing something wrong?

回答1:

Okay, so this is part of what makes mongoid irritating for newcomers. People expect methods like User.all to actually return an array when it really just returns the Criteria object.

In order to provide the syntatic sugar of chainable methods and other fancy query mechanisms, Mongoid seems to use a lazy loading type thing.

You can do:

#array index
User.all[0]

#first/last
User.all.first

#each over things, print out all the users
User.all.each {|u| p u}

#edit, I forgot to include this, which is probably what you really want
#this spits out an array
User.all.to_a

It makes it difficult to quickly verify that things are working for newcomers from ActiveRecord where User.all just returns an array.

回答2:

Try this:

    User.all.first        
    User.find(:first, :conditions => {:first_name => 'John'})    
    User.where(:first_name => 'John').first