脱线道士维克多 - How to use i18n with Rails 4 enums

How to use i18n with Rails 4 enums

利用 Enums，再也不需要用多个布尔值来表示对象的状态了。

class Bug < ActiveRecord::Base
  # Relevant schema change looks like this:
  #
  # create_table :bugs do |t|
  #   t.column :status, :integer, default: 0 # defaults to the first value (i.e. :new)
  # end

  enum status: [ :new, :assigned, :in_progress, :resolved, :rejected, :reopened ]

  belongs_to :assignee, class_name: 'Developer'

  def assignee=(developer)
    if developer && self.new?
      self.status = :assigned
    else
      self.status = :new
    end

    super
  end
end

Bug.resolved            # => a scope to find all resolved bugs
bug.resolved?           # => check if bug has the status :resolved
bug.resolved!           # => update! the bug with status set to :resolved

bug.status              # => a symbol describing the bug's status

# bug.update! status: 3
bug.status = :resolved  # => set the bug's status to :resolved
bug.status = 'resolved' # => set the bug's status to :resolved

# bug.update! status: nil
bug.status = nil
bug.status.nil? # => true
bug.status      # => nil

在内部，与这些状态在数据库中相对应的是整数值，以节省空间。同样值得一提的是，enum 宏所添加的方法是通过 mix-in 一个 module 来实现的。这意味着你可以方便地在 model 中重写它们并使用 super 来调用原来的实现。

使用该特性时还有如下一些注意事项：

一旦定义完 `enum` 的 `symbol` 后，你就不应该再去改动其顺序了。

不要被其名字所迷惑，在一些数据库中并不使用 ENUM 类型来实现该特性。状态和其对应的整数值的匹配是通过 model 文件来维护的。所以一旦定义完 enum 的 symbol 后，你就不应该再去改动其顺序了。可以明确地指定 mapping 来删除不再使用的状态：

class Bug < ActiveRecord::Base
  enum status: {
    new: 0,
    in_progress: 2,
    resolved: 3,
    rejected: 4,
    reopened: 5
  }
end

避免在一个类的不同 enum 中使用相同的名字

class Bug < ActiveRecord::Base
  enum status: [ :new, ... ]
  enum code_review_status: [ :new, ... ] # WARNING: Don't do this!
end

用 scope 来查询 enum 字段：

Conversation.active
Conversation.where(status: [:active, :archived])
Conversation.where.not(status: :active)

如何配合 SimpleForm 和 I18N

# model
class User::Profile < ActiveRecord::Base
  enum gender: [ :female, :male ]
end

# view
= field.input :gender, collection: t_options_for_select(User::Profile, :gender), include_blank: false, wrapper: :horizontal_form

# helper
def t_options_for_select(class_obj, enums_name)
  enums = class_obj.send(enums_name.to_s.pluralize)
  enums.keys.map {|enum| t_enum_option_for_select(enum, class_obj.name.underscore.to_sym, enums_name) }
end

def t_enum_option_for_select(enum, class_name, enum_name)
  [t(enum, scope: [:enumerize, class_name, enum_name]), enum]
end

# config/locales/enumerize.yml
zh:
  enumerize:
    user/profile:
      gender:
        male: "男"
        female: "女"