How to validate text isn't blank in Rails

问题

if I do

  validates :body, :presence => true, :length => {:maximum => 30000, :message => ' is a bit long...'}
  validates :body, :length => {:minimum => 10, :message => ' is a bit short...'}

I still have a possibility of having a text which includes only spaces and /r or /n - non visible chars, which while the text isn't blank by definition, it is blank by looking at it

How can I validate that the text had a min and max length listed above and is also visible (not 10 spaces)

回答1:

Rails adds the handy method blank? which checks for false, nil and empty strings as described here.
Rails also adds the handy validator allow_blank: false.

So in your case it should be:

validates :body, presence: true, allow_blank: false

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Edit (original answer above):

As stated in the answer below, allow_blank: false is not needed as that's the default behaviour of presence: true.

回答2:

presence: true already does that according to http://guides.rubyonrails.org/active_record_validations.html#presence

This helper validates that the specified attributes are not empty. It uses the blank? method to check if the value is either nil or a blank string, that is, a string that is either empty or consists of whitespace.

回答3:

What if you try adding something like this:

validates_format_of :body, :with => /\A[[:graph:]]\Z/i

Notes:

• validates_format_of lets you validate with regex
• [[:graph:]] lets you check a string for printable characters (see "Character Classes")

来源：https://stackoverflow.com/questions/15482354/how-to-validate-text-isnt-blank-in-rails