#!/usr/bin/ruby -w
# answer: http://o...content-available-to-author-only...e.jp/qa/q7067894.html
require 'pp'
h1 = {
"user1" => {"a" => 10, "b" => 20, "c" => 30},
"user2" => {"d" => 5, "e" => 8},
"user3" => {"f" => 15, "g" => 5, "h" => 10}
}
# NG
pp h1.sort_by{|key, value|value.values.inject :-}
# OK
pp h1.sort_by{|key, value|value.values.inject 0, :-}
IyEvdXNyL2Jpbi9ydWJ5IC13CiMgYW5zd2VyOiBodHRwOi8vby4uLmNvbnRlbnQtYXZhaWxhYmxlLXRvLWF1dGhvci1vbmx5Li4uZS5qcC9xYS9xNzA2Nzg5NC5odG1sCgpyZXF1aXJlICdwcCcKCmgxID0gewogICJ1c2VyMSIgPT4geyJhIiA9PiAxMCwgImIiID0+IDIwLCAiYyIgPT4gMzB9LAogICJ1c2VyMiIgPT4geyJkIiA9PiA1LCAiZSIgPT4gOH0sCiAgInVzZXIzIiA9PiB7ImYiID0+IDE1LCAiZyIgPT4gNSwgImgiID0+IDEwfQp9CgojIE5HCnBwIGgxLnNvcnRfYnl7fGtleSwgdmFsdWV8dmFsdWUudmFsdWVzLmluamVjdCA6LX0KCiMgT0sKcHAgaDEuc29ydF9ieXt8a2V5LCB2YWx1ZXx2YWx1ZS52YWx1ZXMuaW5qZWN0IDAsIDotfQ==
[["user1", {"a"=>10, "b"=>20, "c"=>30}],
["user2", {"d"=>5, "e"=>8}],
["user3", {"f"=>15, "g"=>5, "h"=>10}]]
[["user1", {"a"=>10, "b"=>20, "c"=>30}],
["user3", {"f"=>15, "g"=>5, "h"=>10}],
["user2", {"d"=>5, "e"=>8}]]