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module ActiveModel
module Validations
module ClassMethods
# Validates whether the value of the specified attributes are unique across the system. Useful for making sure that only one user
# can be named "davidhh".
#
# class Person < ActiveRecord::Base
# validates_uniqueness_of :user_name, :scope => :account_id
# end
#
# It can also validate whether the value of the specified attributes are unique based on multiple scope parameters. For example,
# making sure that a teacher can only be on the schedule once per semester for a particular class.
#
# class TeacherSchedule < ActiveRecord::Base
# validates_uniqueness_of :teacher_id, :scope => [:semester_id, :class_id]
# end
#
# When the record is created, a check is performed to make sure that no record exists in the database with the given value for the specified
# attribute (that maps to a column). When the record is updated, the same check is made but disregarding the record itself.
#
# Because this check is performed outside the database there is still a chance that duplicate values
# will be inserted in two parallel transactions. To guarantee against this you should create a
# unique index on the field. See +add_index+ for more information.
#
# Configuration options:
# * <tt>:message</tt> - Specifies a custom error message (default is: "has already been taken")
# * <tt>:scope</tt> - One or more columns by which to limit the scope of the uniqueness constraint.
# * <tt>:case_sensitive</tt> - Looks for an exact match. Ignored by non-text columns (+false+ by default).
# * <tt>:allow_nil</tt> - If set to +true+, skips this validation if the attribute is +nil+ (default is: +false+)
# * <tt>:allow_blank</tt> - If set to +true+, skips this validation if the attribute is blank (default is: +false+)
# * <tt>:if</tt> - Specifies a method, proc or string to call to determine if the validation should
# occur (e.g. <tt>:if => :allow_validation</tt>, or <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>). The
# method, proc or string should return or evaluate to a true or false value.
# * <tt>:unless</tt> - Specifies a method, proc or string to call to determine if the validation should
# not occur (e.g. <tt>:unless => :skip_validation</tt>, or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>). The
# method, proc or string should return or evaluate to a true or false value.
def validates_uniqueness_of(*attr_names)
configuration = { :message => ActiveRecord::Errors.default_error_messages[:taken] }
configuration.update(attr_names.extract_options!)
validates_each(attr_names,configuration) do |record, attr_name, value|
# The check for an existing value should be run from a class that
# isn't abstract. This means working down from the current class
# (self), to the first non-abstract class. Since classes don't know
# their subclasses, we have to build the hierarchy between self and
# the record's class.
class_hierarchy = [record.class]
while class_hierarchy.first != self
class_hierarchy.insert(0, class_hierarchy.first.superclass)
end
# Now we can work our way down the tree to the first non-abstract
# class (which has a database table to query from).
finder_class = class_hierarchy.detect { |klass| !klass.abstract_class? }
if value.nil? || (configuration[:case_sensitive] || !finder_class.columns_hash[attr_name.to_s].text?)
condition_sql = "#{record.class.quoted_table_name}.#{attr_name} #{attribute_condition(value)}"
condition_params = [value]
else
# sqlite has case sensitive SELECT query, while MySQL/Postgresql don't.
# Hence, this is needed only for sqlite.
condition_sql = "LOWER(#{record.class.quoted_table_name}.#{attr_name}) #{attribute_condition(value)}"
condition_params = [value.downcase]
end
if scope = configuration[:scope]
Array(scope).map do |scope_item|
scope_value = record.send(scope_item)
condition_sql << " AND #{record.class.quoted_table_name}.#{scope_item} #{attribute_condition(scope_value)}"
condition_params << scope_value
end
end
unless record.new_record?
condition_sql << " AND #{record.class.quoted_table_name}.#{record.class.primary_key} <> ?"
condition_params << record.send(:id)
end
results = finder_class.with_exclusive_scope do
connection.select_all(
construct_finder_sql(
:select => "#{attr_name}",
:from => "#{finder_class.quoted_table_name}",
:conditions => [condition_sql, *condition_params]
)
)
end
unless results.length.zero?
found = true
# As MySQL/Postgres don't have case sensitive SELECT queries, we try to find duplicate
# column in ruby when case sensitive option
if configuration[:case_sensitive] && finder_class.columns_hash[attr_name.to_s].text?
found = results.any? { |a| a[attr_name.to_s] == value }
end
record.errors.add(attr_name, configuration[:message]) if found
end
end
end
end
end
end
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