Question

I’m trying to learn 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

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

I’m trying to do the same, but returning the URLs of the profile pictures of those same users. It returns an array:

["http://www.example.com/example.jpg", "http://www.example2.com/example2.jpg"]

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.

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?

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

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

I’ve also tried this in a view file:

<% for url in @avatars do %>
  <%= puts "#{url}" %>
<% end %>

Which returns:

undefined method `each' for nil:NilClass

Anytime I try to return the strings within an array, they just return an array. Not really sure where to go from here.

Answer 1

app_users = friends.select{ |f| f["is_app_user"] }
@names_and_pictures = app_users.map{ |f| [ f["name"], f["pic_square"] ] }

This creates an array of two-element arrays, i.e.

[ [ "Bob", "http://foo" ], [ "Jim", "http://bar" ] ]

Then you can iterate these in parallel:

<% @names_and_pictures.each do |name,pic_url| %>
  <li><%=name%><img src="<%=pic_url%>"></li>
<% end %>

Note that you don’t use puts in your views, as this function outputs information to the console. Instead, you just use <%= ... %> to coerce Ruby code to be a string value and inject it at the appropriate spot in your output.

---

Your original code is nice (insofar as you’ve wrapped your code in nicely-named methods) but does a little too much.

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

There is no need to puts the names here. The method only happens to return the correct value because each returns the item that was just iterated. Your methods can be written just as effectively as:

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

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

If you happen to want to keep these methods, you can combine two arrays into one by using Array#zip:

names   = friends_realname               # One flat array
avatars = friends_avatars                # Another flat array
@names_and_pictures = names.zip(avatars) # An array of two-element arrays