Question

假设我有以下哈希数组：

arr = [{:name=>"foo", :value=>20},
       {:name=>"bar", :value=>25}, 
       {:name=>"baz", :value=>30}]

我目前按value排序，如下：

arr.sort{|a,b| b[:value] <=> a[:value] }

是否可以在排序后将一个元素（即name == 'bar'）移动到堆栈顶部而不链接另一个方法？理想情况下，这只是排序块中的更多内容。

Answer 1

快速解决方案（我认为可以重构）

arr.sort{|a,b| a[:name] == 'bar' ? -1 : b[:name] == 'bar' ? 1 : b[:value] <=> a[:value] }
# => [{:name=>"bar", :value=>25}, {:name=>"baz", :value=>30}, {:name=>"foo", :value=>20}]

Answer 2

首先，您应该使用Schwartzian transform更简洁（效率更高）Enumerable#sort_by：

arr.sort_by { |h| -h[:value]] }

现在，利用数组定义的lexicographical order，可能会写出您要求的内容：

arr.sort_by { |h| [h[:name] == "bar" ? 0 : 1, -h[:value]] }

Answer 3

arr.sort do |a,b|
  if a[:name] == "bar" && b[:name] != "bar"
    # a is bar but b is not, put a to the top, i.e. a is smaller than b
    -1
  elsif a[:name] != "bar" && b[:name] == "bar"
    # a is not bar but b is, put b to the top, i.e. a is bigger than b
    1
  else
    # both a and b are "bar", or bot are not "bar", than we can sort them normally
    a[:value] <=> b[:value]
  end
end

一个肮脏的解决方案，思考如何写得更好......

按属性和完全匹配对哈希数组进行排序

3 个答案: