Trying to create a specific array in rails3

Question

Lets say I have posts, and posts are created by many different users.

I'm trying to get an array thats 2D, and shows the sum of the posts created by each user. A final array might look like:

[["Jeff",2],["Mike",10],["Jenny",3]]

etc.

I'm trying to create this in my posts model, so something like:

def self.distribution

logic here

end

Thanks!

Pan Thomakos · Accepted Answer · 2011-02-18 17:11:03Z

2

Here is a simple Rails way to do it:

class User
  def self.distribution
    User.
      joins('posts').
      group('users.id').
      select('users.name, count(posts.id) as counter').
      map{ |entry| [entry.name, entry.counter] }
  end
end

User.distribution
=> [["Jeff",2],["Mike",10],["Jenny",3]]

answered Feb 18, 2011 at 17:11

Pan Thomakos

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6 Comments

Elliot Over a year ago

in the view html, the array is rendering the quotes like "&quot;"...I'm using something like this: <%= User.distribution.inspect %>. Any idea how I can make the "'s show up as "?

Pan Thomakos Over a year ago

Yeah, that's because the string is getting sanitized for HTML output. If you don't want to perform string sanitizing, use raw(User.distribution.inspect) or User.distribution.inspect.html_safe. That said, I would recommend you do sanitize the user names, at least, when you output them.

Elliot Over a year ago

Awesome thanks Pan! I have a followup question that I feel like I should post here rather than create a new one.. I only have email addresses stored in the user's table. I do have a profiles table which has the user's name. Is there a way to connect the correct profile and use that for the name in the array?

Pan Thomakos Over a year ago

Yeah, simply add another joins(:profile) and then update your select to do select('profiles.name, count(posts.id) as counter') instead of selecting name from the user table.

Elliot Over a year ago

After everything it works in my local MySQL env, and breaks in Heroku's PG env. sigh

|

Harish Shetty · Accepted Answer · 2011-03-02 05:14:26Z

0

Use the count method in rails.

User.count('posts.id', :include => :posts, :group => "users.name")

The call returns an ordered hash:

#<OrderedHash {"Jeff"=>2, "Mike"=>10, "Jenny"=>1}>

You can convert the result to array:

User.count('posts.id', :include => :posts, :group => "users.name").to_a

The call returns an array:

[["Jeff", 2], ["Mike", 10], ["Jenny", 1]]

edited Mar 2, 2011 at 5:14

answered Feb 18, 2011 at 19:10

Harish Shetty

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2 Comments

Elliot Over a year ago

This seems to be working for me, the only issue now is I'm doing it a little backwards... I'm doing it like this: Post.where(:user_id => @profile.user.id).count('posts.id', :include => :user, :group => "users.email").to_a. Without getting too far into detail, I need that where statement to narrow things down, by post, rather than grabbing all the posts in general. So here is the problem, I store user names in a profile model - linked to the users table (not to the posts table).. Is there a way to get those profile names in this array?

Harish Shetty Over a year ago

I thought you wanted list of users, your filter will return the count for a single user. Other downside of basing the query on Post instead of User is you will not get zero count users.

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