Ruby array.each Returning Same Value Each Time

Question

I'm designing a REST API with Ruby and Sinatra. Only one problem I'm having: I'm trying to iterated over an array of posts selected from MySQL. The format is

[{:post => "Hello, world!", :comments => [{:author => "user1", :content => "Goodbye, world!"}]}, ...]

So, it's an array with a hash with the content post and comments, and the comments key has another array and hash(es) containing the author and content of the comment.

I have the following code pulling an array of posts from MySQL (returned in an array with hashes in it), and then iterating over those hashes. For each hash in the array, it gets the post ID and queries MySQL for any comments associated with that post. It then pushes the post and the comments to a hash, which is the pushed to an array that is returned.

def get_post(id = 'null', profile = 'null', owner = 'null')
        r = Array.new
        x = Hash.new
        p = self.query("SELECT * FROM `posts` WHERE `id` = '#{id}' OR `post_profile` = '#{profile}' OR `post_owner` = '#{owner}'")
        p.each do |i|
            x[:post] = i
            x[:comments] = self.query("SELECT * FROM `comments` WHERE `post` = '#{i["id"]}'")
            r.push(x)
        end
        return r
end

The odd thing is is that I can use a puts statement in the loop, and I'll get the individual posts

Ex:

r.push(x)
    puts x

But the array (r) just contains the same data over and over again. Sorry for such a long post, I just wanted to be thorough.

Chris Heald · Accepted Answer · 2013-06-02 01:27:47Z

2

You keep pushing the same Hash instance onto the array, rather than creating new hashes. Try this:

def get_post(id = 'null', profile = 'null', owner = 'null')
  p = self.query("SELECT * FROM `posts` WHERE `id` = '#{id}' OR `post_profile` = '#{profile}' OR `post_owner` = '#{owner}'")
  p.map do |i|
    {
      post: i,
      comments: self.query("SELECT * FROM `comments` WHERE `post` = '#{i["id"]}'")
    }
  end
end

What this does is loop through the posts (with map rather than each, as I'll explain in a moment), and for each posts, returns a new hash consisting of your desired data. The map method collects all the return values from the loop into an array, so you don't have to do any manual array management.

answered Jun 2, 2013 at 1:27

Chris Heald

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4 Comments

Sam Clark Over a year ago

Okay, I tried that. It lists only the posts in individual hashes. No comments whatsoever.

Chris Heald Over a year ago

Are you sure that you're using map rather than each?

Sam Clark Over a year ago

In other words, the same thing db.query returns.

Sam Clark Over a year ago

Yes: p.map do |i| { post: i, comments: self.query("SELECT * FROM comments WHERE post = '#{i["id"]}'") } end

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