Regural expression with not condition


#1

Hi all,

i’m trying validate the format which doesn’t consist of an empty string
in the single or double quotes.

validates_format_of :name,:with=>/^[’"][ ]*[’"]$/ ,:on=> :create

/^[’"][ ]*[’"]$/ it does validation for like the string ’ ’ and " " . i
need except this like the string may contain “vamsi” or ‘vamsi’ or
“vamsi’s” all these three are valid for me.

so how to modify the above expression is there any thing like
:without? (ofcourse there is no)

or can we put a not condition for the regular expression
like !(/^[’"][ ]*[’"]$/)

Thanks
VK.


#2

On Sat, Jan 24, 2009 at 11:05 PM, Vamsi K. <
removed_email_address@domain.invalid> wrote:

Hi all,

i’m trying validate the format which doesn’t consist of an empty string
in the single or double quotes.

Hi.

How about /^’"[’"]$/.
It will match a single or double quotation mark at the start of the
line,
followed by one or more of any character, followed by a single or double
quotation mark at the end of the line.

Please note that it will match things like “’” (a single quotation mark
inside double quotes) and ‘’’ (a single quotation mark inside single
quotes). You might want to handle such cases or come up with a better
regexp.

BTW, Rubular1 is a great tool for editing and testing regular
expressions.

Regards,
Yaser


#3

Vamsi K. wrote:

i’m trying validate the format which doesn’t consist of an empty string
in the single or double quotes.

validates_format_of :name,:with=>/^[’"][ ]*[’"]$/ ,:on=> :create

/^[’"][ ]*[’"]$/ it does validation for like the string ’ ’ and " " . i
need except this like the string may contain “vamsi” or ‘vamsi’ or
“vamsi’s” all these three are valid for me.

What do you mean: the string may contain spaces, but must not start or
end with one?

so how to modify the above expression is there any thing like
:without? (ofcourse there is no)

Yes there is:
validates_each :name do |record,attr,value|
record.errors.add attr, ‘is invalid’ if value[0] =~ /some_regexp/
end


#4

Vamsi K. wrote:

validates_format_of :name,:with=>/^[’"][ ]*[’"]$/ ,:on=> :create

P.S. WARNING!! Never use ^ and $ in regular expressions which validate
untrusted data. This is because, unlike Perl, they don’t mean “match
start and end of string”, but match start and end of a line within the
string. You need \A and \z to anchor at the start and end of the string.

irb(main):001:0> bad_data = “myname\nrm -rf /"
=> "myname\nrm -rf /

irb(main):002:0> puts “is valid” if bad_data =~ /^[a-z]+$/
is valid
=> nil
irb(main):003:0> puts “is valid” if bad_data =~ /\A[a-z]\z$/
=> nil