Here are some of the smaller yet notable features in the Rails 1.2 release of ActiveRecord made since the 1.1 release. (compiled by Josh Susser).

Finding

Added simple hash conditions to #find that will just convert a hash to an equality/AND-based condition string. Example:

Person.find(:all, :conditions => { :last_name => "Catlin", :status => 1 })

…is the same as:

Person.find(:all, :conditions => [ "last_name = ? and status = ?", "Catlin", 1 ])

This makes it easier to pass in the options from a form or otherwise outside.

Added find_or_initialize_by_X which works like find_or_create_by_X but doesn’t save the newly instantiated record.

Records and arrays of records are bound as quoted ids.

Foo.find(:all, :conditions => ['bar_id IN (?)', bars])
Foo.find(:first, :conditions => ['bar_id = ?', bar])

Associations

Allow :uniq => true with has_many :through associations. This is equivalent to doing a SELECT DISTINCT in SQL, but it is done in Ruby code instead.

Add records to has_many :through using «, push, and concat by creating the join model record. Raise if base or associate are new records since both ids are required to create the association. #build raises an error since you can’t associate an unsaved record. #create! takes an attributes hash and creates both the associated record and its join model record in a transaction.

For example:

# before:
post.taggings.create!(:tag => Tag.find_by_name('finally')
# after:
post.tags << Tag.find_by_name('finally')

And:

# before:
transaction { post.taggings.create!(:tag => Tag.create!(:name => 'general')) }
# after:
post.tags.create! :name => 'general'

Add #delete support to has_many :through associations.

has_one supports the :dependent options :destroy, :delete, and :nullify.

Misc

Support for row-level locking, using either the :lock finder option or the #lock! method. See ActiveRecord::Locking::Pessimistic docs for details.

# Obtain an exclusive lock on person 1 so we can safely increment visits.
Person.transaction do
  # SELECT * FROM people WHERE id=1 FOR UPDATE
  person = Person.find(1, :lock => true)
  person.visits += 1
  person.save!
end