RUBY Grouping data by parsed REST JSON result property - ruby-on-rails

Question

First of all, I am very new to Ruby so go easy on me! I have the parsed JSON in my sourceHash variable and I am trying to group data by the "displayName" property. The JSON format is something like this (I've simplified it without changing the structure):
{
"results": [
{
"id": "12345",
"title": "my blog post",
"history": {
"createdOn": "2017-09-18 15:38:26",
"createdBy": {
"userName": "myUserName",
"displayName": "Michael W."
}
}
},
{ ... same stuff for some other blog post ... },
{ ... same stuff for some other blog post ... },
{ ... same stuff for some other blog post ... }
]
}
Basically, there are two things I want to do.
Imagine this list as "list of blog posts including the author data" of them.
Find the person who posted the most amount of entries
Get the top 10 bloggers, ordered by their blog post count, descending
So the first would look something like this:
Michael W. (51 posts)
However, the second one would look like this:
Michael Wayne (51 posts)
Emilia Clarke (36 posts)
Charlize Theron (19 posts)
Scarlett Johansson (7 posts)
I've played around these queries, trying to merge my LINQ logic into this, but I failed... (I'm a Ruby noob so be easy!)
sourceHash = #mainData["results"]
hashSetPrimary = sourceHash.group_by{|h| h['history']['createdBy']['displayName']}
return hashSetPrimary
So long story short, I am trying to write to separate queries that would group the data by those criteria, any help is appreciated as I can't find any proper way to do it.

Answer 1

Firstly, you need to look at your hash syntax. When you define a hash using h = { "foo": "bar" }, the key is not actually a string, but rather a symbol. Therefore accessing h["foo"] is not going to work (it will return nil); you have to access it as h[:foo].
So addressing that, this does what you need:
sourceHash = #mainData[:results]
hashSetPrimary = sourceHash.group_by{ |h| h.dig(:history, :createdBy, :displayName) }
.map { |k, v| [k, v.count] }
.sort_by(&:last)
return hashSetPrimary
Hash#dig requires Ruby 2.3+. If you are running on a lower version, you can do something like this instead of dig:
h[:history] && h[:history][:createdBy] && h[:history][:createdBy][:displayName]