Question

Hopefully a simple question around a rails best-practice.

Let’s keep this super simple; say I have a task model that has an ID, description and status.

In my controller I have an index action to return all tasks

def index
  @tasks = Task.all
end

My question is, in my view, suppose I want to display the tasks in separate HTML tables according to their status.

What is the best practice?

a) Query the database multiple times in the index action, ie

def index
  @draft_tasks = Task.where(status: "Draft")
  @approved_tasks = Task.where(status: "Approved")
  @closed_tasks = Task.where(status: "Closed")
end

b) Query the database once, and filter in the contoller action

def index
  tasks = Task.all
  @draft_tasks = tasks.#somethinghere
  @approved_tasks = tasks.#somethinghere
  @closed_tasks = tasks.#somethinghere
end

c) Filter in the view

<% @tasks.each do |k, v| %>
  <% some if statement searching for the status I want %>
    # Some code to output the table
  <%end%>
<%end%>

or

d) Something else?

Answer 1

The generally accepted best practices here are to keep controller methods thin and to keep logic out of the view. So with that in mind, one possible way to do this would be:

# model
class Task
  scope :drafts, where(:status => "Draft")
  scope :approved, where(:status => "Approved")
  scope :closed, where(:status => "Closed")
end

# controller
def index
  @draft_tasks = Task.drafts
  @approved_tasks = Task.approved
  @closed_tasks = Task.closed
end

This will make 3 queries to the database, which could become a performance concern down the road, but if that does happen, you can optimize it at the model level (e.g. by defining class methods drafts, approved, and closed where the first one called prefetches everything). It’s less elegant though, so don’t prematurely optimize.