I’m a fan of ActiveRecord’s callbacks, as i see it a clean way to get things done in the life-cycle of a model instance. Yet, today a couple of us just tripped over the following:

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class Thing < ActiveRecord::Base
  before_create :reset_pretty_flag

private

  def reset_pretty_flag
    # Let's KISS for now, even though the logic is flawed :P
    self.pretty = name.downcase.include?('pretty')
  end
end

The problem with Thing#reset_pretty_flag is that in the unfortunate case that thing isn’t pretty, its creation fails. Why ?? Cos when thing isn’t pretty, a false is returned, & this halts the create executation chain. The workaround is therefore to return a true always:

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def reset_pretty_flag
  self.pretty = name.downcase.include?('pretty')
  true # any other non nil/false value will work as well
end

To learn more, i strongly encourage a good read on ActiveRecord’s callbacks