Ruby validation for objects

Question

I have a Author class and need to make some validations before initializing

class Author
  include Validations

  attr_accessor :name, :biography
  

  def initialize(name, biography = nil)
    validate_author

    @name = name
    @biography = biography
  end

  def to_s
    "#{name}\n#{biography}"
  end
end

I use module for this

module Validations
  def validate_author
    raise ::StandardError, 'Name is required' if name.strip.empty?
  end 
end

And i get this error

extentions/validations.rb:8:in `validate_author': undefined method `strip' for nil:NilClass (NoMethodError)

It's ruby application

You tagged your questions with ruby-on-rails. I wonder why you are implementing validations yourself and do not use ActiveModel::Validations? — spickermann
– spickermann, Commented Apr 21, 2021 at 10:05
I would recommend having a look into the DRY ecosystem, which includes dry validations - dry-rb.org/gems/dry-validation/1.5 — dax
– dax, Commented Apr 21, 2021 at 12:21

Santiago Almiron · Accepted Answer · 2021-04-21 12:38:43Z

1

The error gives you the clue, "for nil:NilClass (NoMethodError)", you can't apply the method .split to a Nil, what's happening that you are not passing anything so @name is nil by default, i don't know the rest of the code, but one think that you can do is use the "||" conditional writing something like.

raise ::StandardError, 'Name is required' if name.strip.empty? || name == nil

answered Apr 21, 2021 at 12:38

Santiago Almiron

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Comments

kalifs · Accepted Answer · 2021-04-21 09:12:04Z

0

Name is not yet assigned

class Author
  include Validations

  attr_accessor :name, :biography


  def initialize(name, biography = nil)

    @name = name
    @biography = biography
    validate_author
  end

  def to_s
    "#{name}\n#{biography}"
  end
 end

Or you can pass name to validate_author(name)

answered Apr 21, 2021 at 9:12

kalifs

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Comments

Farhad Ajaz · Accepted Answer · 2021-04-21 09:12:13Z

0

I think because the validate_author runs before setting the name instance variable. So if you move validate_author after setting instance variables, then it should work. However undefined method strip' for nil:NilClass (NoMethodError)` will still be raised as long name is nil.

answered Apr 21, 2021 at 9:12

Farhad Ajaz

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1 Comment

Warden Over a year ago

The thing is that if i just put raise ::StandardError, 'Name is required' if name.strip.empty? before assignment then it works too

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