rails string length validation not working

问题:

I must be missing something basic but I keep getting validation errors:

app/model/person.rb

class Person < ActiveRecord::Base
  attr_accessible  :cell

  before_validation :format_cell_string

  validates :cell, :length => { :is => 10 }

  protected

    def format_cell_string
      self.cell = self.cell.gsub!(/\D/, '') if self.cell != nil
    end

end

In rails c

> bib = Person.new(cell: "1234567890")
> bib.save

leads to a ROLLBACK

bib.errors => #<ActiveModel::Errors:0x007fcb3cf978d8 @base=#<Person id: nil, created_at: nil, updated_at: nil, cell: nil>, @messages={:cell=>["is the wrong length (should be 10 characters)"]}>

Thinking that is could be a rails console or irb error, I also tried in my form to no avail. Trying bib = Person.new, bib.save and then bib.update_attributes(cell: "0123456789") also doesn't work in the console. Am I missing something! I've check the rails docs on validations and the rails api on model validations and tried many different things. Any thoughts? I was using rails 3.2.6 and just upgraded to rails 3.2.7. No change.

回答1:

gsub! modifies the string in place and returns nil if no changes were made:

"1234567890".gsub!(/\D/, '') #=> nil

So in the case where the field contains only digits your code is setting the field to nil before the validation which causes it to fail. Using gsub! on attributes is best avoided generally, as it doesn't play well with Rails' change tracking.

self.cell = self.cell.gsub(/\D/, '') if self.cell != nil

should do the trick