gistfile1.rb

# Wrong!
# If foo is valid but bar is not, foo is still saved.
# This breaks the transactional nature
#
def create
  Foo.transaction do
    @foo = Foo.create(params[:foo])
    @bar = Bar.create(params[:bar])
    if @foo.save and @bar.save
      redirect_to some_url
    else
      render :action => "new"
    end
  end
end

# Right
# Notice how the rescue is outside the transaction.
# This causes the transaction to be rolled back
#
def create
  Foo.transaction do
    @foo = Foo.create(params[:foo])
    @bar = Bar.create(params[:bar])
    @foo.save! and @bar.save!
    redirect_to some_url
  end
rescue ActiveRecord::RecordInvalid => e
  render :action => "new"
end

# Also works
# be careful though since the transaction is not rolled back,
# but the records are never saved
#
def create
  Foo.transaction do
    @foo = Foo.create(params[:foo])
    @bar = Bar.create(params[:bar])
    if @foo.valid? and @bar.valid?
      @foo.save! and @bar.save!
      redirect_to some_url
    else
      render :action => "new"
    end
  end
end