活動記錄實例中的所有查詢

Question

也許有人知道我該如何解決以下問題：

我有一個模型，想查詢它。

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

我該如何解決？

編輯：

示例：MyModel有一個名稱。 我有四個MyModel實例

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

我現在要：

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

我相信這可以滿足您的要求。

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

Answer 2

一種可能的解決方案是利用ActiveRecord :: Relation實例響應許多Array實例方法的事實：

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

但是，這將返回Array的一個實例，因此您無法繼續追加其他范圍。 由您決定是否適合您的情況。