Rails枚举验证失败

Question

The code below is a simplified version of a polymorphic model that uses enums however I am struggling with the validation.

The last line of the model is the problem validation.

This works:

validates_inclusion_of  :value, in: Vote.values.keys

This does not work returning an error:

validates_inclusion_of  :value, in: vote_options.keys

Error

ActiveRecord::RecordInvalid: Validation failed: Value is not included in the list

Model:

class Vote < ApplicationRecord
    belongs_to :voteable, polymorphic: true

    vote_options  = {vote_no: 0, vote_yes: 1}
    enum value: vote_options

    validates_inclusion_of  :value, in: vote_options.keys
end

Update:

class Vote < ApplicationRecord
    belongs_to :voteable, polymorphic: true

    VOTE_OPTIONS  = HashWithIndifferentAccess.new({ vote_no: 0, vote_yes: 1 }).freeze
    EMOJI_OPTIONS = HashWithIndifferentAccess.new({thumb_up: 2, thumb_down: 3, happy_face: 4, sad_face: 5}).freeze

    enum value: HashWithIndifferentAccess.new.merge(VOTE_OPTIONS).merge(EMOJI_OPTIONS)

    validates_inclusion_of  :value, in: vote_options.keys
end

Update2:

class Like < ApplicationRecord
    belongs_to :likeable, polymorphic: true

    VOTE_OPTIONS  = { vote_no: 0, vote_yes: 1 }.freeze
    EMOJI_OPTIONS = { thumb_up: 2, thumb_down: 3, happy_face: 4, sad_face: 5 }.freeze

    enum value: VOTE_OPTIONS.merge(EMOJI_OPTIONS)

    with_options :if => :is_meeting? do |o|
        o.validates_uniqueness_of :user_id, scope: [:likeable_id, :likeable_type], message: "You have already voted on this item."
        o.validates_inclusion_of  :value, in: HashWithIndifferentAccess.new(VOTE_OPTIONS).keys
    end

    with_options :if => :is_comment? do |o|
        o.validates_uniqueness_of :user_id, scope: [:likeable_id, :likeable_type], message: "You can only tag once."
        o.validates_inclusion_of  :value, in: HashWithIndifferentAccess.new(EMOJI_OPTIONS).keys
    end

    def is_meeting?
        self.likeable_type == "Meeting"
    end

    def is_comment?
        self.likeable_type == "Comment"
    end

end

Answer 1

The reason for this behavior is that enum converts the passed-in hash into a HashWithIndifferentAccess . This is a special ActiveSupport extension to a normal Hash that treats its symbol and string keys the same .

Now, your vote_options definition uses symbols but ActiveRecord internally uses strings when setting enum values to db record attributes. When validating the record with the Vote.values.keys variant, it all works even though it is comparing a string value (in the attribute) to a symbol key in the enum definition, because Vote.values will return the hash with indifferent access created in the enum definition.

On the contrary, if you use vote_options.keys for your validation, it will fail because it compares string values with symbols and these are not the same things in Ruby.

To overcome this and still use a class variable (actually, I'd suggest a freezed constant instead here), use a hash with indifferent access too :

VOTE_OPTIONS = HashWithIndifferentAccess.new({ vote_no: 0, vote_yes: 1 }).freeze
enum value: VOTE_OPTIONS

validates_inclusion_of :value, in: VOTE_OPTIONS.keys

Update - multiple merged hashes - you only have to declare a HashWithIndifferentAccess where you actually need it, you can use simple hashes in other places:

VOTE_OPTIONS  = { vote_no: 0, vote_yes: 1 }.freeze
EMOJI_OPTIONS = { thumb_up: 2, thumb_down: 3, happy_face: 4, sad_face: 5 }.freeze

enum value: VOTE_OPTIONS.merge(EMOJI_OPTIONS)

validates_inclusion_of :value, in: HashWithIndifferentAccess.new(VOTE_OPTIONS).keys