Is it possible to format data as it comes out of the database in Rails?

Question

In rails I have data already in my database. I would like for certain things to be formatted certain ways no matter where it displays in my app. An example might be a social security number. In the database it might be stored as 123456789, but I want to display it as 123-45-6789 anywhere it shows up.

I know that I can format the output using string manipulation, but I wanted to know if there was a better way so that if I were to use,

<%= user.ssn %>

It would automatically get formatted correctly.

Update:

After much, MUCH research on my part, I came across the "lazy" way. You can override the default getter using the following in the User model.

def ssn
  read_attribute(:ssn).insert(5, '-').insert(3, '-')
end

My utter ignorance of proper terminology prevented me from finding this more easily. This sort of the is referred to as overriding a method and is discussed in the Rails documentation here.

All that being said I'll be writing a helper method which I originally thought of, but wanted to see if there was an easier way (i.e. less code writing). In the process I learned a lot about ActiveRecord, so my time not wasted. :-)

Other references:

score 1 · Answer 1 · answered Feb 01 '14 at 05:33

1

The correct way would be something like what Richard said where you manipulate in some sort of ViewModel/PageObject/Decorator/Blahblah. The Rails way would be to use a helper method. The lazy way is to override your ssn getter in the User model to format super

Now you need to decide what kind of developer you are :]

answered Feb 01 '14 at 05:33

Logan Serman

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I ultimately chose the helper method way as my answer, but I found this answer to be the most helpful in my growth as a developer. Thanks :-) – josephbales Feb 01 '14 at 16:07

Richard Jordan · Answer 2 · 2014-02-01T05:53:32.480

Use a view model. A bit like a presenter which is often done to add presentation logic, but which speaks the language of the view, a view model talks the language of the model but is just a simple decorator.

Instead of just passing an instance of user

@user = User.find(params[:id])

You would do something like

user = User.find(params[:id]
@user = UserView.new(user)

When I use a View Model it's usually a PORO decorate adding a few methods or overriding methods on User.

Here's a sample from a real application of mine, adapted to your question:

class ViewModelBase < SimpleDelegator

  def self.view_for(name)
    define_method(name) { __getobj__ }
  end

  def class
    __getobj__.class
  end
end


class UserView < ViewModelBase
  view_for :user

  def formatted_ssn
    formatting_rules(user.ssn)
  end

  def formatting_rules(ssn)
    # some rules for formatting an ssn
  end
end

Wow, just wow. I'm new to Rails and haven't heard of this approach yet. I will have to look into this some more. Thanks for the education. — josephbales, Feb 01 '14 at 16:03

score 0 · Accepted Answer · answered Feb 01 '14 at 11:00

The standard approach is to create an Helper.

def format_ssn(value)
  # apply the transformation
end

<%= format_ssn(user.ssn) %>

If you want the value to always be outputted in that way, you can also consider to provide an alternative method in the model

class User
  def formatted_ssn
    # transform and return user.ssn
  end
end

You may see examples of people overriding the getter of ssn to properly format the value, but I strongly suggest you to avoid that approach. It may cause the formatted value to be stored in the database, overriding the original one.

Thanks for the response. This app is only going to be dealing with archived data, so I won't be writing to the database, but I'm going to take your advice anyway. This will be helpful to me in the future. — josephbales, Feb 01 '14 at 16:00

Is it possible to format data as it comes out of the database in Rails?

Update:

3 Answers3