Rails separate array items with comma inside partial

Question

What is the most elegant way in Rails to create a comma-separated list inside a partial?

I've just recently discovered that you can use partials to iterate through a collection sent from another view template. So in the view template I have:

<% render @dvd.director %> 

Then in /view/directors/_director.html.erb:

<%= director.director %>

This actually does something like:

@dvd.director.each { |d| puts d.director }

Now, I know I could use a .join like so:

<% @dvd.director.map { |t| t.director }.join(", ") %>

But since the partial already iterates through each entry in the array, how can I separate the lists properly and not have the last one (or a single one) with an ugly comma at the end?

A lot of entries will have only one director, I just want to separate those that have more than one properly. I know I can do all this manually (using a normal, non-iterating partial and creating the .each loop myself), but am trying to do it, and learn, the Rails way.

Thanks.

Edit

To try to explain a little better, @dvd.director returns an ActiveRelation object like so:

[#<Director id: 13, director: "Andrew Stanton">, #<Director id: 14, director: "Lee Unkrich">]

So I can't just do @dvd.director.join(', ')

Is there another way to get that data other than

@dvd.director.each { |dir| dir.director }

Because there I have the same problem, I have to count them or make sure it's not the last item before I put a comma between them, or extract just the director names and put them into a string or something like that. If I could do a join it would be great.

Answer 1

Ruby's join method won't add the separator character if there is only a single element in the array.

You should be able to do the following for a list of any size:

@dvd.director.map(&:director).join(", ")