How to call parameters for 'format' and 'with' option in models?

Yoochan,

The with method expects a Regular Expressions pattern to match against. If you are looking to do a little bit of formatting to the profile_name field before validations occur (so that you can remove whitespace elegantly, versus erring out), you can perform a before_validation callback.

before_validation :remove_whitespace

def remove_whitespace
  self.profile_name = profile_name.gsub(' ', '')
end

Now, if all goes well, this method will be called before any validations occur. Thus you can modify the parameters before they're judged.

As far as your validation is concerned. I would suggest you go back to using a RegEx pattern. One like the following:

validates :profile_name,  presence: { message: I18n.t('errors.messages.blank') }, 
                          format: { with: /^[a-zA-Z0-9]+$/, message: 'must be formatted correctly.' }

That pattern is saying: "only allow letters and numbers, of any case, and nothing else." The carot (^) tells RegEx that this is the beginning. And the dollar sign ($) tells RegEx that the end has been reached. The plus sign (+) requires RegEx match the preceding pattern at least one time in order to be successful.