Tell, Don't Ask when dealing with displaying model attributes or a null replacement

Question

I have the following model:

# == Schema Information
#
# Table name: clients
#
#  id         :integer          not null, primary key
#  first_name :string(255)
#  last_name  :string(255)
#  email      :string(255)
#

class Client < ActiveRecord::Base
  def full_name
    if first_name.blank? && last_name.blank?
      'Name: unknown'
    else
      first_name + ' ' + last_name
    end
  end

  def email_address
    email.blank? ? 'Email: unknown' : email
  end
end

Which has the following spec:

RSpec.describe Client, type: :model do

  describe 'full_name' do
    it 'should return first_name + last_name if not blank' do
      @client = create(:client, first_name: 'John', last_name: 'Doe')
      @client.full_name.should == 'John Doe'
    end

    it "should return 'Name: unkonwn' if name is blank" do
      @client = create(:client, first_name: '', last_name: '')
      @client.full_name.should == 'Name: unknown'
    end
  end

  describe 'email_address' do
    it 'should return email if email is not blank' do
      @client = create(:client, email: '[email protected]')
      @client.email_address.should == '[email protected]'
    end

    it "should return 'Email: unkonwn' if email is blank" do
      @client = create(:client, email: '')
      @client.email_address.should == 'Email: unknown'
    end
  end
end

As you can see I am creating methods (email_address, full_name) to display attributes (or a combination of attributes) in views. If the attribute is blank I want to return a string saying the value is unknown.

I have many more attributes that I would like to display this way, but it seems inefficient to come up with alternative method names for methods that simply return the attribute or the "blank alternative".

As an example, these are some of the other attributes: sex, age, source. Rather than calling client.sex or client.age I would create a method and call client.name_of_sex or client.age_string -- it starts to get awkward (I went from email to email_address in the above example).

The alternative I know is to put logic in my views:

<% if client.email.blank? %>
  Email: unknown
<% else %>
  <%= client.email %>
<% end %>

This is inappropriate for a number of reasons, but my current alternative (the example above) doesn't seem to be optimal.

Is this a point where I should get into making a view-model? Is there some other way I could elegantly perform the actions I want? Or is the way I'm doing it a reasonable thing to do (I'm going to have a lot of attributes I want to display this way)?

Answer 1

I want to offer an alternative to helpers because I believe in this particular case using a presenter to isolate view logic is better than using helpers. As stated yourself you have many more attributes, so having a presenter class avoids having to write generic methods and gives you a scalable way to handle view complexity.

You can use a gem like Draper, or roll your own, which I prefer.

class UserPresenter
  attr_reader :user, :template

  def initialize(user, template)
    @user, @template = user, template
  end

  def full_name
    handle_none user.name, "Name not provided" do
      user.first_name + ' ' + user.last_name
    end
  end

  def email
    handle_none user.email, "Email not provided"
  end

  def gender
    handle_none user.gender
  end

private

  def handle_none(attribute, message = nil, &block)
    if attribute.present?
      block_given? ? yield : attribute
    else
      message || "Not Available"
    end
  end
end

Then, using a helper method, you can instantiate this in the view:

  def present(user)
    presenter = UserPresenter.new(user, self)
    yield presenter if block_given?
    presenter
  end

And in the view:

- present @user do |presenter|
  = link_to presenter.full_name, @user, class: 'whatever'

Answer 2

Definitely, this does not belong in the model. The orthodox way is to create a helper. Note how you can use the pattern Object#presence:

module ApplicationHelper
  def show_field(field, value)
    value.presence || "#{field}: unknown"
  end
end

And use it in the views:

<%= show_field("Name", user.full_name) %>

You can go a step further and use OOP view presenters if you like the idea (personally I don't use them).

Answer 3

I think what you are searching for is an Option type. For more information and an implementation see here and here.

Explaination: Your model seems to have to deal not just with user names only but rather with two cases: there is a user name and there is none. To handle this, you should change your model in that it does not save a user name (as string) and using a blank name as as special case but rather to save a datatype that either contains a user name (as string) or that doesn't.

You can then create a new type that uses an Option type and prints its value if it is there or "unknown" if it is not.

Answer 4

Instead of:

if first_name.blank? && last_name.blank?
  'Name: unknown'
else
  first_name + ' ' + last_name
end

One who prefers one-liners could do:

"#{first_name} #{last_name}".strip.empty? ? "Name: unknown" : "#{first_name} #{last_name}"

Furthermore, it's better to move such code to a helper method or a decorator using https://github.com/drapergem/draper