Question

I have a restrictive schema (i.e. the schema already has null restrictions and maximum length etc). Would putting all of them in the model also overkill and counterproductive?…

  validates :CouponID,      :presence => true,
                            :numericality => true

  validates :MerchantName,  :presence => true,
                            :length => { :maximum => 100 }

  validates :MerchantID,    :presence => true,
                            :numericality => true

  validates :Network,       :length => { :maximum => 20 }

  validates :Label,         :presence => true

  validates :CouponCode,    :length => { :maximum => 100 }

  validates :EndDate,       :presence => true

  validates :Link,          :presence => true

  validates :Status,        :presence => true,
                            :length => { :maximum => 45 }

  validates :Country,       :length => { :maximum => 100 }

Answer 1

No it’s not an overkill. Putting these into validators your model would allow Rails to catch them before inserting them into the database. It’s also good design and practice.

If you omitted these, you would get MySQL errors thrown instead.

For example. Let’s say I have a Comment model which contains an attribute string called body which can not be nil in my table.

class Comment < ActiveRecord::Base
end

If I tried:

comment = Comment.create(body: nil)

I would get the following exception.

ActiveRecord::StatementInvalid: Mysql2::Error: Column 'body' cannot be null:

This is bad. The natural flow of your application would break.

But, if I put the validators in my model like so

class Comment < ActiveRecord::Base
  validates :body, presence: true
end

and tried the following:

comment = Comment.create(body: nil)

I would not get an exception thrown but the errors array for my variable to tell me what went wrong.

comment.errors.full_messages
=> ["Body can't be blank"]

It’s good practice to put validators in your models and allows for good design.