If your application has forms to edit string fields, you probably want to strip the entered values (remove whitespace from beginning and end). The reason is that your users will copy + paste values from unholy places (websites, Microsoft Office) and end up having trailing whitespace in most of their records.

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Because browsers ignore whitespace, no one will usually notice this until you get the weirdest bug reports (e.g. two seemingly equal records are not, or multiple records for "unique" values).

Use the attached trait in your model to have it automatically strip all :string fields before validation:

class Organisation < ActiveRecord::Base
  validates_presence_of :name, :city, :phone, :website, ....
  does 'strip_string_fields'
end

Attributes of other types (including :text) are not stripped.

Stripping whitespace from existing records

If you have existing data that needs to be cleaned, do it in a migration, using MySQL's TRIM function:

class StripWhitespaceFromOrganisation < ActiveRecord::Migration
  def change
    update 'UPDATE organisations SET name = TRIM(name), city = TRIM(city), ...'
  end
end