How do you sort an array alphabetically using sort_by in ruby?

Question

I have an array of memberships. In each membership is a group. I need to sort this array of memberships by the name of the group. I've tried a bunch of different ways, and the latest way is this:

@memberships.sort_by! { |m| m.group.name }

However, this doesn't sort by the name. It appears to be randomly sorting the array.

Membership belongs_to :group
Group has_many :memberships

@memberships is equal to:

[
  {
  id: 2141,
  user_id: 491,
  group_id: 271,
  member_type: "member",
    group: {
      id: 271,
      name: "Derek's",
      privacy: "open",
      bio_image_url: "/bio_images/medium/missing.png?1340285189",
      member_count: 1,
      upcoming_checkins_count: 0
    }
  },
  {
  id: 2201,
  user_id: 221,
  group_id: 291,
  member_type: "member",
    group: {
      id: 291,
      name: "Rounded Developement",
      privacy: "closed",
      bio_image_url: "/groups/medium/291/bioimage.jpg?1340736175",
      member_count: 7,
      upcoming_checkins_count: 0
   }
}
]

NOTE: This does work --> @memberships.sort_by! { |m| m.group.id }

It will order the array based on the group.id so maybe it has something to do with sorting alphabetically?

Any help would be much appreciated.

score 71 · Accepted Answer · answered Jul 17 '12 at 21:46

71

Wow, after struggling with this for an extremely long time, I realized my problem was a simple one. I was sorting by group.name but some of the group names were uppercase and some were lower, which was throwing it all off. Converting everything to downcase worked well.

@memberships.sort_by!{ |m| m.group.name.downcase }

answered Jul 17 '12 at 21:46

Brian Weinreich

7,692
8
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1

Award yourself the answer when the system will let you. – the Tin Man Jul 17 '12 at 22:28
Downcase is the way to go +1 – earlonrails Mar 26 '13 at 21:35
The `.downcase` method is very important because other wise the sorting stuff will behave weird for some elements. – alexventuraio May 29 '22 at 18:51

Angelo · Answer 2 · 2012-07-17T21:31:03.137

3

Is the sort method an option?

ary.sort{ |a,b| a[:group][:name] <=> b[:group][:name] }

edited Jul 17 '12 at 21:31

answered Jul 17 '12 at 21:24

Angelo

492
3
5

I tried that as well.. `@memberships.sort { |a,b| a.group.name <=> b.group.name }` still doesn't work tho. – Brian Weinreich Jul 17 '12 at 21:28
Forgot the nesting... I corrected by adding the parent group key – Angelo Jul 17 '12 at 21:31
Okay, maybe this is the problem– something I didn't mention. When I do a.group.name I am performing a join between the memberships and groups table. So, would that have an effect on the result sorting? Cause it still won't work with the updated code. – Brian Weinreich Jul 17 '12 at 21:33
So you're not sorting the resulting array of hashes, but the ActiveRecord objects, correct? Maybe try using "order" `Membership.joins(:groups).order("groups.name")` – Angelo Jul 17 '12 at 21:52
I ended up figuring it out. It was a stupid problem. I didn't realize sort didn't take into account upper and lower case. So I could figure out why it looked like this: [Ash, Bob, Jim, anna, kim] – I ended up sorting by downcase. Thanks for your help (sorry to bother ya with something silly like this!) – Brian Weinreich Jul 18 '12 at 14:39

score 1 · Answer 3 · answered Jul 17 '12 at 21:27

1

I don't see how your code is working. I can't access the hashes in the arrays using m.group.name

Here's a working syntax

@memberships.sort_by!{ |m| m[:group][:name] }

answered Jul 17 '12 at 21:27

Dty

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ah, i think i should revise my question. when i do m.group i am performing a sql join – Brian Weinreich Jul 17 '12 at 21:30
in any case, that still doesn't correctly sort by name. it appears to be random (im sure there is a method to its madness). – Brian Weinreich Jul 17 '12 at 21:38

How do you sort an array alphabetically using sort_by in ruby?

3 Answers3