对象数组：拒绝除最大值之外的所有对象

Question

我有一组Mortgage对象

class Mortgage
  attr_accessor :rate, :deposit

  def initialize(deposit, rate)
    @deposit = deposit
    @rate = rate
  end
end

我想拒绝任何抵押贷款的比率高于另一笔抵押贷款的抵押贷款。

例如，想象一下以下抵押贷款数组

Mortgage 1, :rate => 3, :deposit => 20
Mortgage 2, :rate => 5, :deposit => 20
Mortgage 3, :rate => 7, :deposit => 30

该方法应拒绝抵押2。

Answer 1

mortgages = [
  Mortgage.new(20, 3),
  Mortgage.new(20, 5),
  Mortgage.new(30, 7)
]

mortgages.group_by(&:deposit).map { |deposit, mortgages| mortgages.min_by(&:rate) }

group_by根据给定的方法构造一个哈希值，因此在这种情况下它给出：

{
  20 => [
          #<Mortgage:0x24 @rate=3 @deposit=20>,
          #<Mortgage:0x2c @rate=5 @deposit=20>
        ],

  30 => [
          #<Mortgage:0x38 @rate=7 @deposit=30>
        ]
}

然后，只需按每笔存款的最低费率抵押即可。