从类 << self 中动态定义范围答案

【问题标题】：Dynamically define scopes from within class << self从类 << self 中动态定义范围
【发布时间】：2013-10-31 19:02:28
【问题描述】：

如何在 class << self 上下文中动态分配范围？

class Partner < ActiveRecord::Base

  STATUS = {
    pending: 0,    # 0 account has a pending billing request (but is not yet open)
    active: 1,     # 1 account has an active base subscription
    suspended: 2,  # 2 account has been suspended (e.g. after a base subscription decline)
    expired: 3,    # 3 base subscription has expired
    incomplete: 4, # 4 partner application process incomplete
    closed: 5,     # 5 account has been permanently closed
    cancelled: 6   # 6 account has been cancelled by user (but is still unexpired)
  }

  after_initialize :setup_status_enums

  def status
    STATUS.key(read_attribute(:status))
  end

  def status=(s)
    write_attribute(:status, STATUS[s])
  end

  private

    def setup_status_enums
          class << self
            STATUS.map do |key, val|
              raise "Collision in enum values method #{key}" if respond_to?("#{key.to_s}?") or respond_to?("#{key.to_s}!") or respond_to?("#{key.to_s}")

              define_method "#{key.to_s}?" do
                send("status") == key
              end

              define_method "#{key.to_s}!" do
                send("status=", val)
              end

              scope key.to_sym, lambda { where(:status => val) }
            end
          end
    end

end

【问题讨论】：

标签： ruby ruby-on-rails-4 rails-activerecord named-scope

【解决方案1】：

这样的事情应该可以工作。您可以直接在类定义中遍历您的 STATUS 哈希。

class Partner < ActiveRecord::Base
  STATUS = {
    pending: 0,    # 0 account has a pending billing request (but is not yet open)
    active: 1,     # 1 account has an active base subscription
    suspended: 2,  # 2 account has been suspended (e.g. after a base subscription decline)
    expired: 3,    # 3 base subscription has expired
    incomplete: 4, # 4 partner application process incomplete
    closed: 5,     # 5 account has been permanently closed
    cancelled: 6   # 6 account has been cancelled by user (but is still unexpired)
  }

  STATUS.each do |key, val|
    define_method "#{key.to_s}?" do
      status == key
    end

    define_method "#{key.to_s}!" do
      status = val
    end

    scope key, lambda { where(status: val) }
  end

  ...
end

【讨论】：

【解决方案2】：

您似乎正在寻找状态机。

在 Ruby 中，查看 state_machine 或 aasm gems。然后，您可以根据state 列定义范围（或者您可以命名为status。）

状态机还将帮助您管理状态之间的转换，因此您可以仅针对特定转换或状态运行回调或验证。

【讨论】：