I am doing some client side validation in ASP.NET MVC and I found myself trying to do conditional validation on a set of items (ie, if the checkbox is checked then validate and visa versa). This was problematic, to say the least.
To get around this, I figured that I could "cheat" by having a hidden element that would contain all of the information for each set, thus the idea of a CSV string containing this information.
I already use a custom [HiddenRequired] attribute to validate if the hidden input contains a value, with success, but I thought as I will need to validate each piece of data in the csv, that a regular expression would solve this.
My regular expression work is extremely weak and after a good 2 hours I've almost given up.
This is an example of the csv string:
true,3,24,over,0.5
to explain:
true denotes if I should validate the rest. I need to conditionally switch in the regex using this
3 and 24 are integers and will only ever fall in the range 0-24.
over is a string and will either be over or under
0.5 is a decimal value, of unknown precision.
In the validation, all values should be present and at least of the correct type
Is there someone who can either provide such a regex or at least provide some hints, i'm really stuck!
Try this regex:
#"^(true,([01]?\d|2[0-4]),([01]?\d|2[0-4]),(over|under),\d+\.?\d+|false.*)$"
I'll try to explain it using comments. Feel free to ask if anything is unclear. =)
#"
^ # start of line
(
true, # literal true
([01]?\d # Either 0, 1, or nothing followed by a digit
| # or
2[0-4]), # 20 - 24
([01]?\d|2[0-4]), # again
(over|under), # over or under
\d+\.?\d+ # any number of digits, optional dot, any number of digits
| #... OR ...
false.* # false followed by anything
)
$ # end of line
");
I would probably use a Split(',') and validate elements of the resulting array instead of using a regex. Also you should watch out for the \, case (the comma is part of the value).
Related
I've been looking for a good way to see if a string of items are all numbers, and thought there might be a way of specifying a range from 0 to 9 and seeing if they're included in the string, but all that I've looked up online has really confused me.
def validate_pin(pin)
(pin.length == 4 || pin.length == 6) && pin.count("0-9") == pin.length
end
The code above is someone else's work and I've been trying to identify how it works. It's a pin checker - takes in a set of characters and ensures the string is either 4 or 6 digits and all numbers - but how does the range work?
When I did this problem I tried to use to_a? Integer and a bunch of other things including ranges such as (0..9) and ("0..9) and ("0".."9") to validate a character is an integer. When I saw ("0-9) it confused the heck out of me, and half an hour of googling and youtube has only left me with regex tutorials (which I'm interested in, but currently just trying to get the basics down)
So to sum this up, my goal is to understand a more semantic/concise way to identify if a character is an integer. Whatever is the simplest way. All and any feedback is welcome. I am a new rubyist and trying to get down my fundamentals. Thank You.
Regex really is the right way to do this. It's specifically for testing patterns in strings. This is how you'd test "do all characters in this string fall in the range of characters 0-9?":
pin.match(/\A[0-9]+\z/)
This regex says "Does this string start and end with at least one of the characters 0-9, with nothing else in between?" - the \A and \z are start-of-string and end-of-string matchers, and the [0-9]+ matches any one or more of any character in that range.
You could even do your entire check in one line of regex:
pin.match(/\A([0-9]{4}|[0-9]{6})\z/)
Which says "Does this string consist of the characters 0-9 repeated exactly 4 times, or the characters 0-9, repeated exactly 6 times?"
Ruby's String#count method does something similar to this, though it just counts the number of occurrences of the characters passed, and it uses something similar to regex ranges to allow you to specify character ranges.
The sequence c1-c2 means all characters between c1 and c2.
Thus, it expands the parameter "0-9" into the list of characters "0123456789", and then it tests how many of the characters in the string match that list of characters.
This will work to verify that a certain number of numbers exist in the string, and the length checks let you implicitly test that no other characters exist in the string. However, regexes let you assert that directly, by ensuring that the whole string matches a given pattern, including length constraints.
Count everything non-digit in pin and check if this count is zero:
pin.count("^0-9").zero?
Since you seem to be looking for answers outside regex and since Chris already spelled out how the count method was being implemented in the example above, I'll try to add one more idea for testing whether a string is an Integer or not:
pin.to_i.to_s == pin
What we're doing is converting the string to an integer, converting that result back to a string, and then testing to see if anything changed during the process. If the result is =>true, then you know nothing changed during the conversion to an integer and therefore the string is only an Integer.
EDIT:
The example above only works if the entire string is an Integer and won’t properly deal with leading zeros. If you want to check to make sure each and every character is an Integer then do something like this instead:
pin.prepend(“1”).to_i.to_s(1..-1) == pin
Part of the question seems to be exactly HOW the following portion of code is doing its job:
pin.count("0-9")
This piece of the code is simply returning a count of how many instances of the numbers 0 through 9 exist in the string. That's only one piece of the relevant section of code though. You need to look at the rest of the line to make sense of it:
pin.count("0-9") == pin.length
The first part counts how many instances then the second part compares that to the length of the string. If they are equal (==) then that means every character in the string is an Integer.
Sometimes negation can be used to advantage:
!pin.match?(/\D/) && [4,6].include?(pin.length)
pin.match?(/\D/) returns true if the string contains a character other than a digit (matching /\D/), in which case it it would be negated to false.
One advantage of using negation here is that if the string contains a character other than a digit pin.match?(/\D/) would return true as soon as a non-digit is found, as opposed to methods that examine all the characters in the string.
I'm using Rails and Nokogiri and I'm trying to parse some website.
This is where I'm stuck:
doc.css('#example > li:nth-child(1)').each do |node|
money = node.xpath('//*ul/li/div/span').text
end
It returns something like:
$100,000£230,000$40,000$9,000€600$800,000
I want to split those items, save them to the database and finally hand them to the view.
So, in the view, I want it to appear like:
(1)$100,000
(2)£230,000
(3)$40,000
(4)$9,000
(5)€600
(6)$800,000
I tried to split those items by this code below.
money = node.xpath('//*ul/li/div/span').text.split(/[$€£]/)
but the result looks like this:
["", "100,000", "230,000", "40,000", "9,000", "600", "800,000"]
And I don't know which item is in Dollar, Euro, or Pond.
Is there any good way to solve this problem?
you're almost there,
just use the positive lookahead :)
irb(main):005:0> "$100,000£230,000$40,000$9,000€600$800,000".split(/(?=[$£€])/)
=> ["$100,000", "£230,000", "$40,000", "$9,000", "€600", "$800,000"]
It needs a regular expression. This works:
"$100,000£230,000$40,000$9,000$600$800,000".scan(/([^\d][0-9,]+)/)
=> [["$100,000"],
["£230,000"],
["$40,000"],
["$9,000"],
["$600"],
["$800,000"]]
The regex contains these parts:
[^\d]: A character class matching a single non-digit. This will match the currency symbol.
`[0-9,]+': Another character class, this time repeating (the '+'). It matches the numeric part (0-9) plus the thousand's separator.
Hi I've been struggling with this for the last hour and am no closer. How exactly do I strip everything except numbers, commas and decimal points from a rails string? The closest I have so far is:-
rate = rate.gsub!(/[^0-9]/i, '')
This strips everything but the numbers. When I try add commas to the expression, everything is getting stripped. I got the aboves from somewhere else and as far as I can gather:
^ = not
Everything to the left of the comma gets replaced by what's in the '' on the right
No idea what the /i does
I'm very new to gsub. Does anyone know of a good tutorial on building expressions?
Thanks
Try:
rate = rate.gsub(/[^0-9,\.]/, '')
Basically, you know the ^ means not when inside the character class brackets [] which you are using, and then you can just add the comma to the list. The decimal needs to be escaped with a backslash because in regular expressions they are a special character that means "match anything".
Also, be aware of whether you are using gsub or gsub!
gsub! has the bang, so it edits the instance of the string you're passing in, rather than returning another one.
So if using gsub! it would be:
rate.gsub!(/[^0-9,\.]/, '')
And rate would be altered.
If you do not want to alter the original variable, then you can use the version without the bang (and assign it to a different var):
cleaned_rate = rate.gsub!(/[^0-9,\.]/, '')
I'd just google for tutorials. I haven't used one. Regexes are a LOT of time and trial and error (and table-flipping).
This is a cool tool to use with a mini cheat-sheet on it for ruby that allows you to quickly edit and test your expression:
http://rubular.com/
You can just add the comma and period in the square-bracketed expression:
rate.gsub(/[^0-9,.]/, '')
You don't need the i for case-insensitivity for numbers and symbols.
There's lots of info on regular expressions, regex, etc. Maybe search for those instead of gsub.
You can use this:
rate = rate.gsub!(/[^0-9\.\,]/g,'')
Also check this out to learn more about regular expressions:
http://www.regexr.com/
I need to match only strings that include one character / between numbers or integer numbers.
Examples:
1 YES
1/2 YES
some_text NO
some/test NO
some NO
2///2 NO
/12 NO
1/2/ NO
1.2/3 NO
Edit:
By rubular.com i`m tried to check this regex: /\d+(\/\d+)?
How regex should looks like?
If you're only including whole numbers or fractions:
\d+(\/\d+)?
If you also want to allow decimals:
\d+(\.\d+)?(\/\d+(\.\d+)?)?
Edit: Note that I'm making a lot of assumptions about what you really want. Bart Kiers's comments to your question are very important -- I took the liberty of assuming that what you want is numbers. If that isn't true, please clarify the question.
Edit2: I'm also making one more important assumption. Your question says "strings that include / or integer number." If you want to make sure that the string is ONLY a number and nothing else, then add ^ to the beginning of the line and $ to the end. Example:
^\d+(\/\d+)?$
What is the regular expression to check a cost has been provided correctly:
Number must be greater than or equal to 0.01
Number must be less than or equal to 99.99
Possible matches are:
9 | 23.3 | 25.69
Not allowed:
| 2.
Of course, the correct way would be to take the provided string, convert it to a number (catching errors if it's not a parseable number) and then compare that with the valid values.
If it has to be a regex, it's of course possible but ugly:
^(?:[1-9][0-9]?(?:\.[0-9]{1,2})?|0?.0[1-9]|0?.[1-9][0-9]?)$
Explanation:
^ # start of string
(?: # either match
[1-9][0-9]? # a number between 1 and 99
(?:\.[0-9]{1,2})? # optionally followed by a decimal point and up to two digits
| # or
0?.0[1-9] # a number between 0.01 and 0.09 (optionally without leading 0)
| # or
0?.[1-9][0-9]? # a number between 0.1 and 0.99
) # end of alternation
$ # end of string
Of course, in most regex dialects, you can use \d in place of [0-9] without a change in meaning, but I think in this case sticking to the longer version helps readability.
In Ruby, assuming your input string never contains a newline:
if subject =~ /^(?:[1-9][0-9]?(?:\.[0-9]{1,2})?|0?.0[1-9]|0?.[1-9][0-9]?)$/
# Successful match
else
# Match attempt failed
end
Since you care about the number of significant digits, another solution would be to first check if the input looks like a number, and if it passes that test, convert it to a float and check if it's in range.
^(\d{1,2}|\d{0,2}\.\d{1,2})$
would match any number (integer or decimal up to two digits after the decimal point) between 0 and 99.99. Then you just need to check whether the number is >= 0.01. The advantage of this approach is that you can easily extend the range of digits allowed before/after the decimal point if the requirements for valid numbers change, and then adjust the value check accordingly.
I am not sure you need to do this using regular expression why dont you just split the string on '|' into an array and check each element in array is greater than 0.01 and less than 99.99
A solution using a regexp would be hard to maintain since it is a very strange and unintuitive way to solve the problem. It would be hard for anyone reading your code (including yourself in a couple of weeks) to understand what the purpose of the check is.
That said, assuming values 0.00 - 99.99 are valid, the regexp could be
^\d{0,2}(\.\d\d?)?$
Assuming 0.01 - 99.99, it's a bit more complicated:
^0{0,2}(\.(0[1-9]|[1-9]\d?))?|\d{0,2}(\.\d\d)?$
And don't get me started on 0.02 - 99.98... :-)
So basically, don't do this. Convert the string to a numerical value and then do a regular interval check.
try
^\d{1,2}(\.\d{1,2})?$
it checks whether there are 1 or 2 digits and optionally if there is a dot it checks if there are 1 or 2 digits after the dot.
as answer to the comments of your question: nothing speaks against checking for the format before sending the request to a server or something else. range checks could be done somewhere else.
It's not the best but works
(0\.01|0\.02|0\.03| ... |99\.98|99\.99)
Since you're in Rails, you might be better served using validates_numericality_of in your model:
validates_numericality_of :cost, :greater_than_or_equal_to => 0.01,
:less_than_or_equal_to => 0.99
To prevent fractional pennies, use this in conjunction with validates_format_of:
validates_format_of :cost, :with => /\A\d*(\.\d{1,2})?\Z/
This leverages the strength of each validation.