RoR: how to deal with information in arrays

Question

Ok, so I'm trying to fool around with the koala gem - to link facebook with my ruby on rails application. I'm starting to get the hang of it, but I'm running into some serious mental blocks!

  def friends
    facebook.fql_query("SELECT uid,username, is_app_user, name,     pic_square FROM user WHERE uid IN(SELECT uid2 FROM friend WHERE     uid1 = me()) AND is_app_user=1");
  rescue Koala::Facebook::APIError => e
    logger.info e.to_s
    nil
  end

So, firstly, I'm using the FQL to search through a users friends. It returns a hash of details of users who are friends of current_user (the one signed into the app) - and that have also connected with my application.

  def friends_realname
     names = friends.select {|f| f["is_app_user"] }.map {|f| f["name"]}
     names.each { |name| puts name}
  end

Here, I'm selecting the above "user's friends also using my app's" names - and mapping them into an array. This returns an array: ["friend1's name", "friend2's name"]

def friends_avatars
    @avatars = friends.select {|f| f["is_app_user"] }.map {|f| f["pic_square"]}
end

Here, I'm trying to do the same - but returning the URLs of the profile pictures of those same users. It returns an array of ["http://www.example.com/example.jpg", "http://www.example2.com/example2.jpg"]

Here's where I'm stuck. I want to format the information from the returned arrays. So for the real names - instead of returning the actual array, I want to return a list of names. And obviously for the images, instead of returning an array of image urls - I actually want to 'puts' those images out in the view.

So, I'm thinking that I need to iterate through each of these arrays, and then use the .each method to do something with each string in the array - e.g puts img_tag? As I said, if anyone can help with some example code, I'd really appreciate it :)

Would something like this be possible?:

  def friends_avatars
    @avatars = friends.select {|f| f["is_app_user"] }.map {|f| f["pic_square"]}
    @avatars.each { |avatar| puts image_tag "#{avatar}}"}
  end

Cheers, Sam

EDIT: Just realised that image_tag is a helper method, so I can't use it there.

Answer 1 · 2013-01-08T16:25:16Z

January 8, 2013 4:25pm

Hey Sam,

This is a loaded question but I think you're on the right track. Personally, I'd take a slightly different approach to this and use the items as a hash structure instead.

First, I'd rename the friends method so it's a little more representative of what we're asking for:

def facebook_friends_query
  facebook.fql_query("SELECT uid,username, is_app_user, name,     pic_square FROM user WHERE uid IN(SELECT uid2 FROM friend WHERE     uid1 = me()) AND is_app_user=1");
rescue Koala::Facebook::APIError => e
  logger.info e.to_s
  nil
end

Now we can create a friends method which uses that query method. Don't forget to write tests to make sure that the method we wrote above works:

def friends
  @friends ||= facebook_friends_query.select{|f| f["is_app_user"] }
end

Now we have a friends method we can iterate through. The first thing we do is assign it to a variable with the conditional assignment operator. That will assign a value to a variable if it does not already have one. This way, the second time it runs it will return the friends. Also, we're reusing the f["is_app_user"] in the two examples above so we just shorten it to one method.

Now we're free to iterate over the friends hash and have access to the information it provides:

friends.each do |friend|
  puts "Name: #{friend['name']}"
  puts "Avatar: #{friend['pic_square']}"
  puts "Avatar image tag: <img alt="#{friend['name']}" src='#{friend['pic_square]}' />"
end

Disclaimer: I've never used the Koala gem and this code may not work, but hopefully this makes sense :)

Answer 2 · 2013-01-08T16:48:57Z

January 8, 2013 4:48pm

Hey Jason, really appreciate your help! It does indeed make sense :) The code you've suggested works perfectly :) Although, I do think I'm putting my code in the wrong places (model/view/controller)!

After I typed out this question, I spent all night fiddling around with things, and I ran into A LOT of errors. The main one was with regards to my variables (global or instance) being NilClass. Then when I tried to iterate through, what I thought was a hash or array (using .each for example) - I got back a NoMethod error.

I tried a few things - creating simple variables (e.g array = Array.new, or array = [ ]) - and use the class method on those variables - still NillClass. This has really confused me - as when I use the same .class method in IRB - I get back what I expect. I feel like this is a really important part of Rails variables that I'm just not clicking with - any ideas? When that variable is within a method - and I call class on that method - it is correct however, is this just the way that rails works?

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RoR: how to deal with information in arrays

2 Answers

Jason Seifer

Jason Seifer