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100 lines
3.5 KiB
Ruby
100 lines
3.5 KiB
Ruby
module ActiveRecord
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# Declare an enum attribute where the values map to integers in the database, but can be queried by name. Example:
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#
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# class Conversation < ActiveRecord::Base
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# enum status: [ :active, :archived ]
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# end
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#
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# # conversation.update! status: 0
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# conversation.active!
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# conversation.active? # => true
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# conversation.status # => "active"
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#
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# # conversation.update! status: 1
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# conversation.archived!
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# conversation.archived? # => true
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# conversation.status # => "archived"
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#
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# # conversation.update! status: 1
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# conversation.status = "archived"
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#
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# You can set the default value from the database declaration, like:
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#
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# create_table :conversations do |t|
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# t.column :status, :integer, default: 0
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# end
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#
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# Good practice is to let the first declared status be the default.
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#
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# Finally, it's also possible to explicitly map the relation between attribute and
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# database integer with a +Hash+:
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#
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# class Conversation < ActiveRecord::Base
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# enum status: { active: 0, archived: 1 }
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# end
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#
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# Note that when an +Array+ is used, the implicit mapping from the values to database
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# integers is derived from the order the values appear in the array. In the example,
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# <tt>:active</tt> is mapped to +0+ as it's the first element, and <tt>:archived</tt>
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# is mapped to +1+. In general, the +i+-th element is mapped to <tt>i-1</tt> in the
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# database.
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#
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# Therefore, once a value is added to the enum array, its position in the array must
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# be maintained, and new values should only be added to the end of the array. To
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# remove unused values, the explicit +Hash+ syntax should be used.
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#
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# In rare circumstances you might need to access the mapping directly.
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# The mappings are exposed through a constant with the attributes name:
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#
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# Conversation::STATUS # => { "active" => 0, "archived" => 1 }
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#
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# Use that constant when you need to know the ordinal value of an enum:
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#
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# Conversation.where("status <> ?", Conversation::STATUS[:archived])
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module Enum
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def enum(definitions)
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klass = self
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definitions.each do |name, values|
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# DIRECTION = { }
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enum_values = _enum_methods_module.const_set name.to_s.upcase, ActiveSupport::HashWithIndifferentAccess.new
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name = name.to_sym
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_enum_methods_module.module_eval do
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# def direction=(value) self[:direction] = DIRECTION[value] end
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define_method("#{name}=") { |value|
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unless enum_values.has_key?(value)
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raise ArgumentError, "'#{value}' is not a valid #{name}"
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end
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self[name] = enum_values[value]
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}
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# def direction() DIRECTION.key self[:direction] end
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define_method(name) { enum_values.key self[name] }
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pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
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pairs.each do |value, i|
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enum_values[value] = i
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# scope :incoming, -> { where direction: 0 }
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klass.scope value, -> { klass.where name => i }
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# def incoming?() direction == 0 end
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define_method("#{value}?") { self[name] == i }
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# def incoming! update! direction: :incoming end
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define_method("#{value}!") { update! name => value }
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end
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end
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end
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end
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private
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def _enum_methods_module
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@_enum_methods_module ||= begin
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mod = Module.new
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include mod
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mod
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end
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end
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end
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end
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