如何在 ruby 中通过两对"键 => 值"过滤哈希数组？

Question

我有一个哈希数组：

array = [
{:created_at => 1520913341, :event_id => '111', :album_id => '123'},
{:created_at => 1520740541, :event_id => '234', :album_id => '999'},
{:created_at => 1520654141, :event_id => '111', :album_id => '777'},
{:created_at => 1520394941, :event_id => '233', :album_id => '444'},
{:created_at => 1520049341, :event_id => '890', :album_id => '765'}
 ]

我需要保留所有:event_id的哈希值，如果:event_id重复，请保留最早:created_at的哈希值。如何在红宝石中做到这一点？

我希望得到以下响应：

[
{:created_at => 1520740541, :event_id => '234', :album_id => '999'},
{:created_at => 1520654141, :event_id => '111', :album_id => '777'},
{:created_at => 1520394941, :event_id => '233', :album_id => '444'},
{:created_at => 1520049341, :event_id => '890', :album_id => '765'}
 ]

Answer 1

array.sort_by { |h| h[:created_at] }.uniq { |h| h[:event_id] }
  #=> [{:created_at=>1520049341, :event_id=>"890", :album_id=>"765"},
  #    {:created_at=>1520394941, :event_id=>"233", :album_id=>"444"},
  #    {:created_at=>1520654141, :event_id=>"111", :album_id=>"777"},
  #    {:created_at=>1520740541, :event_id=>"234", :album_id=>"999"}]

参见 Array#uniq，特别是"按顺序遍历self，并保留第一个出现。

Answer 2

试试这个

array.group_by { |t| t[:event_id] }.map { |_,hash| hash.min_by { |t| t[:created_at]} }.sort_by {|t| -t[:created_at]}