Adding a virtual field to an object

Question

  def list_links_count do

    query = 
      from l in Link,
        join: c in Click, as: :click,
        where: c.link_id == l.id,
        group_by: l.id,
        select: {l, count(l.id)}

    query |> Repo.all

  end

I've got a function that counts that number of clicks per link. The problem is with the final data structure, which is of the form {Link, 10}. What I'd really like to do is have it put_in the total, so I can access it more easily in a view, something like link.click_count. Is that possible?

Answer 1

Do you have the virtual field on your Ecto schema for Link? If not, you'll want to add it:

field(:click_count, :integer, virtual: true)

Then your select could look something like this:

select: %{l | click_count: count(l.id)}

Since you now have a click_count key in your Link structs, you can put that key and still have a list of Links. So you should be able to access link.click_count.

Answer 2

Use Kernel.elem/2:

{Link, 10} |> elem(1) 
#⇒ 10

So, within your code:

query
|> Repo.all()
|> how_do_you_get_tuple()
|> elem(1)