在Virtus Ruby对象中使用String或Hash初始化

Question

我需要能够创建一个基于Virtus的对象，接受一个哈希或字符串。如果它是一个哈希，那么正常的行为就是完美的。如果它是一个普通字符串，那么我需要将它转换为{'id' => "STRING"}。此时，我不确定如何/在哪里重写initialize方法来执行此功能。或者也许有一种不同的方式。非常感谢您的专业知识。

class Contact
  include Virtus.model

  attribute :id, String
end

class Account
  include Virtus.model

  attribute :id, String
  attribute :contact, Contact
  attribute :name, String
end 

account = Account.new("1234")
account.id #>1234

# and still work like this

account = Account.new(id: '1234', contact: '123456', name: 'Bob Jones')
account.id #>1234
account.contact.id #>123456
account.name #>Bob Jones

样本数据

{'id' => '1234', 'contact' => '123456', 'name' => 'Bob Jones'}

所以在联系人和客户之间。我需要它们能够用一个字符串初始化，这个字符串填充了@id参数。

Answer 1

Virtus’ author’s opinion的问题是你不应该使用Virtus进行清理。正如你从@engineersmnky的回答中看到的，覆盖initialize方法需要更多的工作。

相反，包装你传入的对象会更容易：

class Hashable
  def initialize(hashable_object)
    @obj = hashable_object
  end

  def to_hash
    case @obj
    when Hash then @obj
    when String
      { "id" => @obj }
    else
      raise "No conversion from #{@obj.class} to hash"
    end
  end
end

Account.new(Hashable.new(relationship))

Answer 2

注意：这仅用于启迪目的，可能会产生难以调试的意外后果。

如果您确实想这样做，您可以像这样覆盖Virtus::InstanceMethods::Constructor：

module VirtusOverride
  def self.included(base)
    raise "#{base.name} must include Virtus.model prior to including VirtusOverride" unless base.included_modules.include?(Virtus::InstanceMethods)
  end

  def initialize(*attributes)
    super(construct(attributes))
  end

  private
    def construct(attributes)
      return attributes.first if valid_constructor?(attributes)
      build_attributes_from_array(attributes) 
    end 
    def valid_constructor?(attributes)
      return false unless attributes.count == 1 
      constructor = attributes.first
      constructor.is_a?(Hash) &&  
      !(attribute_set.flat_map {|a| [a.name,a.name.to_s]} & constructor.keys).empty?
    end
    def build_attributes_from_array(attributes)
      attribute_set.map(&:name).zip(attributes).to_h
    end
end 

然后根据需要将其包括在内

class Account
  include Virtus.model
  include VirtusOverride

  attribute :id, String
  attribute :contact, Hash
end 

现在，您可以将选项positional传递给属性定义(例如Account.new(id,contact))或作为Hash传递。

示例：

Account.new("1234",{name: 'mnky'})
#=> #<Account:0x2a071b8 @id="1234", @contact={:name=>"mnky"}>

Account.new(id: "1234", contact: {name: 'mnky'})
#=> #<Account:0x2b42b78 @id="1234", @contact={:name=>"mnky"}>

你可以给Virtus::InstanceMethods::Constructor打补丁来实现同样的效果，但我并不是一个很支持这种哲学的人，因为这可能会给其他开发人员带来困惑，因为模块的包含提供了粒度和清晰度。

更新

class Account
  include Virtus.model
  include VirtusOverride

  attribute :id, String
  attribute :contact, Contact
end 

class Contact
  include Virtus.model
  include VirtusOverride

  attribute :id, String
end  

 Account.new(id: '1234', contact: '123456', name: 'Bob Jones')
 #=>  #<Account:0x2bcb060 @id="1234", @contact=#<Contact:0x2bc9c50 @id="123456">, @name="Bob Jones">
 Account.new('1234', '123456', 'Bob Jones')
 #=> #<Account:0x2faea00 @id="1234", @contact=#<Contact:0x2fae880 @id="123456">, @name="Bob Jones">
 Account.new('id' => '1234', 'contact' => '123456', 'name' => 'Bob Jones')
 #=> #<Account:0x2faffc0 @id="1234", @contact=#<Contact:0x2fafb70 @id="123456">, @name="Bob Jones">