How do I write a regex in my Rails model validation? - regex

Question

I'm using Rails 5. I want one of the attributes in my model to fail validation if it consists of only letters or if it contains the pattern "\d:\d" anywhere in its value. I tried this
validates_format_of :my_attr, numericality: { greater_than: 0, :only_integer => true }, :allow_blank => true, :without => /(\d:\d|^\p{L}+$)/
But when I create a new object
2.4.0 :018 > ab = MyObjectTime.new({:my_attr => "ab"})
It is not indicating an error when I query "ab.errors" for the field in question. What's the correct way to write the regular expression above?

Answer 1

First and Foremost new method does not trigger any kind of validation on the object.
class Person < ApplicationRecord
validates :name, presence: true
end
>> p = Person.new
# => #<Person id: nil, name: nil>
>> p.errors.messages
# => {}
new method does not trigger any validation on an object as it is not hitting the database to save the record.
>> p.save
# => false
save method will try to create the record to the database and triggers the respective validation on the object.
>> p.valid?
# => false
When you hit the .valid? the method, it validates the object against the mentioned validation.
>> p.errors.messages
# => {name:["can't be blank"]}
>> p = Person.create
# => #<Person id: nil, name: nil>
Creating and saving a new record will send an SQL INSERT operation to the database.
Internal functionality of Person.create is Person.new and Person.save
When you are creating an object, it tries to create the valid record to the database and triggers the respective validation.
>> p.errors.messages
# => {name:["can't be blank"]}
>> p.save
# => false
>> p.save!
# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank
>> Person.create!
# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank
Secondly, validates_numericality_of and validates_format_of are the different set of validation helpers which you have mixed.
validates_numericality_of :my_attr, :only_integer => true, :allow_blank => true,
:greater_than => 0
validates_format_of :my_attr, :without => /(\d:\d|^\p{L}+$)/
This validation won't accept any such object :
MyObjectTime.new({:my_attr => "ab"})
MyObjectTime.new({:my_attr => "1:1"})
For more information you can take help from these validation helpers => http://api.rubyonrails.org/classes/ActiveModel/Validations/HelperMethods.html

Answer 2

Try something like this
validates :email, presence: true, format: { with: /\A([^\}\{\]\[#\s\,]+)#((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i }