ruby-on-rails - 活动记录来自实例的所有查询

Question

也许有人知道我如何解决以下问题：

我有一个模型并想查询它。

def MyModel < ActiveRecord::Base

  # instance method
  def all
    my_models = MyModel.all
    my_models.?? # order my_models ActiveRecord::Relation, that the instance which calls the .all instance method is at first position, and the rest is sorted somehow,..whatever.
  end

end

我怎么能解决这个问题？

编辑：

示例：MyModel 有一个名称。我有四个 MyModel 实例

MyModel.all => #<ActiveRecord::Relation [#<MyModel id: 1, name: "name1">, #<MyModel id: 2, name: "name2">, #<MyModel id: 3, name: "name3">, #<MyModel id: 4, name: "name4">]>

我现在想要：

MyModel.find(1).all => #<ActiveRecord::Relation [#<MyModel id: 1, name: "name1">, #<MyModel id: 2, name: "name2">, #<MyModel id: 3, name: "name3">, #<MyModel id: 4, name: "name4">]>

MyModel.find(2).all => #<ActiveRecord::Relation [#<MyModel id: 2, name: "name2">, #<MyModel id: 1, name: "name1">, #<MyModel id: 3, name: "name3">, #<MyModel id: 4, name: "name4">]>

MyModel.find(3).all => #<ActiveRecord::Relation [#<MyModel id: 3, name: "name3">, #<MyModel id: 1, name: "name1">, #<MyModel id: 2, name: "name2">, #<MyModel id: 4, name: "name4">]>

Answer 1

我相信这可以满足您的要求。

def all
  self.class.order("case when id = #{id} then 0 else id end")
end

Answer 2

一个可能的解决方案是利用 ActiveRecord::Relation 实例响应许多 Array 实例方法的事实：

def all
  ary = self.class.order(:id)
  ary = ary.unshift(self)
  ary.uniq
end

但是，这会返回一个 Array 实例，因此您不能继续附加其他范围。由您决定在您的情况下是否可以接受。