Ruby-on-rails – Rails where condition using NOT NIL

arelrails-activerecordruby-on-rails

Using the rails 3 style how would I write the opposite of:

Foo.includes(:bar).where(:bars=>{:id=>nil})

I want to find where id is NOT nil. I tried:

Foo.includes(:bar).where(:bars=>{:id=>!nil}).to_sql

But that returns:

=> "SELECT     \"foos\".* FROM       \"foos\"  WHERE  (\"bars\".\"id\" = 1)"

That's definitely not what I need, and almost seems like a bug in ARel.

Best Answer

The canonical way to do this with Rails 3:

Foo.includes(:bar).where("bars.id IS NOT NULL")

ActiveRecord 4.0 and above adds where.not so you can do this:

Foo.includes(:bar).where.not('bars.id' => nil)
Foo.includes(:bar).where.not(bars: { id: nil })

When working with scopes between tables, I prefer to leverage merge so that I can use existing scopes more easily.

Foo.includes(:bar).merge(Bar.where.not(id: nil))

Also, since includes does not always choose a join strategy, you should use references here as well, otherwise you may end up with invalid SQL.

Foo.includes(:bar)
   .references(:bar)
   .merge(Bar.where.not(id: nil))

Related Solutions

Ruby-on-rails – How to find where a method is defined at runtime

This is really late, but here's how you can find where a method is defined:

http://gist.github.com/76951

# How to find out where a method comes from.
# Learned this from Dave Thomas while teaching Advanced Ruby Studio
# Makes the case for separating method definitions into
# modules, especially when enhancing built-in classes.
module Perpetrator
  def crime
  end
end

class Fixnum
  include Perpetrator
end

p 2.method(:crime) # The "2" here is an instance of Fixnum.
#<Method: Fixnum(Perpetrator)#crime>

If you're on Ruby 1.9+, you can use source_location

require 'csv'

p CSV.new('string').method(:flock)
# => #<Method: CSV#flock>

CSV.new('string').method(:flock).source_location
# => ["/path/to/ruby/1.9.2-p290/lib/ruby/1.9.1/forwardable.rb", 180]

Note that this won't work on everything, like native compiled code. The Method class has some neat functions, too, like Method#owner which returns the file where the method is defined.

EDIT: Also see the __file__ and __line__ and notes for REE in the other answer, they're handy too. -- wg

Ruby-on-rails – Rails: How to set default values in ActiveRecord

There are several issues with each of the available methods, but I believe that defining an after_initialize callback is the way to go for the following reasons:

default_scope will initialize values for new models, but then that will become the scope on which you find the model. If you just want to initialize some numbers to 0 then this is not what you want.
Defining defaults in your migration also works part of the time... As has already been mentioned this will not work when you just call Model.new.
Overriding initialize can work, but don't forget to call super!
Using a plugin like phusion's is getting a bit ridiculous. This is ruby, do we really need a plugin just to initialize some default values?
Overriding after_initialize is deprecated as of Rails 3. When I override after_initialize in rails 3.0.3 I get the following warning in the console:

DEPRECATION WARNING: Base#after_initialize has been deprecated, please use Base.after_initialize :method instead. (called from /Users/me/myapp/app/models/my_model:15)

Therefore I'd say write an after_initialize callback, which lets you default attributes in addition to letting you set defaults on associations like so:

  class Person < ActiveRecord::Base
    has_one :address
    after_initialize :init

    def init
      self.number  ||= 0.0           #will set the default value only if it's nil
      self.address ||= build_address #let's you set a default association
    end
  end

Now you have just one place to look for initialization of your models. I'm using this method until someone comes up with a better one.

Caveats:

For boolean fields do:

self.bool_field = true if self.bool_field.nil?

See Paul Russell's comment on this answer for more details
If you're only selecting a subset of columns for a model (ie; using select in a query like Person.select(:firstname, :lastname).all) you will get a MissingAttributeError if your init method accesses a column that hasn't been included in the select clause. You can guard against this case like so:

self.number ||= 0.0 if self.has_attribute? :number

and for a boolean column...

self.bool_field = true if (self.has_attribute? :bool_value) && self.bool_field.nil?

Also note that the syntax is different prior to Rails 3.2 (see Cliff Darling's comment below)

Best Answer

Related Solutions

Ruby-on-rails – How to find where a method is defined at runtime

Ruby-on-rails – Rails: How to set default values in ActiveRecord

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