How to sort a ruby array by two conditions

Question

I want to sort this array by two different conditionals.

First I want to sort the array by type: A type can be either (1,2,3,4) and I want to sort them in this order 4 - 1 - 2 - 3.

Then within each different type I want to sort them by a percentage descending.

So a sorted array would look like this:

[
  <OpenStruct percent=70, type=4>,
  <OpenStruct percent=60, type=4>,
  <OpenStruct percent=50, type=4>,
  <OpenStruct percent=73, type=1>,
  <OpenStruct percent=64, type=1>,
  <OpenStruct percent=74, type=2>
]ect

How can I accomplish this sort? Currently I can only sort by type descending.

array = array.sort_by {|r| r.type }

Why you wanna 4 to go first? Does it make sense to rename types and change 4 to 1, if 4 should always go first? — Misha Slyusarev
– Misha Slyusarev, Commented Apr 24, 2015 at 19:49

Anthony · Accepted Answer · 2015-04-24 21:44:51Z

3

This should do it:

require 'ostruct'
arr = [
  OpenStruct.new(percent: 73, type: 1),
  OpenStruct.new(percent: 70, type: 4),
  OpenStruct.new(percent: 60, type: 4),
  OpenStruct.new(percent: 50, type: 4),
  OpenStruct.new(percent: 64, type: 1),
  OpenStruct.new(percent: 74, type: 2)
]


puts arr.sort_by { |a| [a.type % 4, -a.percent] }

output:

#<OpenStruct percent=70, type=4>
#<OpenStruct percent=60, type=4>
#<OpenStruct percent=50, type=4>
#<OpenStruct percent=73, type=1>
#<OpenStruct percent=64, type=1>
#<OpenStruct percent=74, type=2>

edited Apr 24, 2015 at 21:44

answered Apr 24, 2015 at 19:47

Anthony

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1 Comment

the Tin Man Over a year ago

Don't use sort for this. It will be much slower than an implementation using sort_by. See stackoverflow.com/a/2651028/128421 and compare the equivalent sort and sort_by tests.

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