ruby-on-rails - 可以在 Rails 中有条件地链接作用域吗？

Question

考虑这段代码:

class Car
  scope :blue, -> { where(color: "blue") }
  scope :manual, -> { where(transmission: "manual") }
  scope :luxury, -> { where("price > ?", 80000) }
end

def get_cars(blue: false, manual: false, luxury: false)
  cars = Car.all
  cars = cars.blue if blue
  cars = cars.manual if manual
  cars = cars.luxury if luxury
end

有没有办法像 Car.blue.manual.luxury 那样有条件地链接这些作用域？ IE。只有参数为真时才作用域？

Answer 1

您可以使用 yield_self( read more here )，这是 ruby​​ 2.5 为它添加的新功能。

在你的例子中:

class Car
  scope :blue, -> { where(color: "blue") }
  scope :manual, -> { where(transmission: "manual") }
  scope :luxury, -> { where("price > ?", 80000) }
end

def get_cars(blue: false, manual: false, luxury: false)
  cars = Car.all
            .yield_self { |cars| blue ? cars.blue : cars }
            .yield_self { |cars| manual ? cars.manual : cars }
            .yield_self { |cars| luxury ? cars.luxury : cars }
end