How to validate an url on the iPhone

Question

In an iPhone app I am developing, there is a setting in which you can enter a URL, because of form & function this URL needs to be validated online as well as offline.

So far I haven't been able to find any method to validate the url, so the question is;

How do I validate an URL input on the iPhone (Objective-C) online as well as offline?

Solution 1

Thanks to this post, you can avoid using RegexKit. Here is my solution (works for iphone development with iOS > 3.0) :

- (BOOL) validateUrl: (NSString *) candidate {
    NSString *urlRegEx =
    @"(http|https)://((\\w)*|([0-9]*)|([-|_])*)+([\\.|/]((\\w)*|([0-9]*)|([-|_])*))+";
    NSPredicate *urlTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", urlRegEx]; 
    return [urlTest evaluateWithObject:candidate];
}

If you want to check in Swift my solution given below:

 func isValidUrl(url: String) -> Bool {
        let urlRegEx = "^(https?://)?(www\\.)?([-a-z0-9]{1,63}\\.)*?[a-z0-9][-a-z0-9]{0,61}[a-z0-9]\\.[a-z]{2,6}(/[-\\w@\\+\\.~#\\?&/=%]*)?$"
        let urlTest = NSPredicate(format:"SELF MATCHES %@", urlRegEx)
        let result = urlTest.evaluate(with: url)
        return result
    }

Solution 2

Why not instead simply rely on Foundation.framework?

That does the job and does not require RegexKit :

NSURL *candidateURL = [NSURL URLWithString:candidate];
// WARNING > "test" is an URL according to RFCs, being just a path
// so you still should check scheme and all other NSURL attributes you need
if (candidateURL && candidateURL.scheme && candidateURL.host) {
  // candidate is a well-formed url with:
  //  - a scheme (like http://)
  //  - a host (like stackoverflow.com)
}

According to Apple documentation :

URLWithString: Creates and returns an NSURL object initialized with a provided string.

+ (id)URLWithString:(NSString *)URLString

Parameters

URLString : The string with which to initialize the NSURL object. Must conform to RFC 2396. This method parses URLString according to RFCs 1738 and 1808.

Return Value

An NSURL object initialized with URLString. If the string was malformed, returns nil.

Solution 3

Instead of writing your own regular expressions, rely on Apple's. I have been using a category on NSString that uses NSDataDetector to test for the presence of a link within a string. If the range of the link found by NSDataDetector equals the length of the entire string, then it is a valid URL.

- (BOOL)isValidURL {
    NSUInteger length = [self length];
    // Empty strings should return NO
    if (length > 0) {
        NSError *error = nil;
        NSDataDetector *dataDetector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:&error];
        if (dataDetector && !error) {
            NSRange range = NSMakeRange(0, length);
            NSRange notFoundRange = (NSRange){NSNotFound, 0};
            NSRange linkRange = [dataDetector rangeOfFirstMatchInString:self options:0 range:range];
            if (!NSEqualRanges(notFoundRange, linkRange) && NSEqualRanges(range, linkRange)) {
                return YES;
            }
        }
        else {
            NSLog(@"Could not create link data detector: %@ %@", [error localizedDescription], [error userInfo]);
        }
    }
    return NO;
}

Solution 4

My solution with Swift:

func validateUrl (stringURL : NSString) -> Bool {

    var urlRegEx = "((https|http)://)((\\w|-)+)(([.]|[/])((\\w|-)+))+"
    let predicate = NSPredicate(format:"SELF MATCHES %@", argumentArray:[urlRegEx])
    var urlTest = NSPredicate.predicateWithSubstitutionVariables(predicate)

    return predicate.evaluateWithObject(stringURL)
}

For Test:

var boolean1 = validateUrl("http.s://www.gmail.com")
var boolean2 = validateUrl("https:.//gmailcom")
var boolean3 = validateUrl("https://gmail.me.")
var boolean4 = validateUrl("https://www.gmail.me.com.com.com.com")
var boolean6 = validateUrl("http:/./ww-w.wowone.com")
var boolean7 = validateUrl("http://.www.wowone")
var boolean8 = validateUrl("http://www.wow-one.com")
var boolean9 = validateUrl("http://www.wow_one.com")
var boolean10 = validateUrl("http://.")
var boolean11 = validateUrl("http://")
var boolean12 = validateUrl("http://k")

Results:

false
false
false
true
false
false
true
true
false
false
false

Solution 5

use this-

NSString *urlRegEx = @"http(s)?://([\\w-]+\\.)+[\\w-]+(/[\\w- ./?%&=]*)?";

View more solutions

Comments

[hpique]

I might be wrong, but I believe that regex doesn't validate urls with query strings or named anchors.

[chris]

You have a small typo. Should be ... and candidateURL.host. Nice solution.

[imnk]

best and most elegant solution

[Thizzer]

You could make the prefix part optional by replacing (http|https):// with ((http|https)://)* but this would allow a very wide variety of urls

[Alex Reynolds]

+1. This is much better than a regex, for the simple reason that a regex is fragile and adds complexity. An NSURL instance is either valid or nil, yielding a quick, simple yes/no answer about the validity of the URL.

[Diego Barros]

I agree with some of the others here. This is a much better solution that fiddling around with regular expressions. This should be the correctly checked answer.

[Thizzer]

This solution doesn't prevent all malformed urls from being returned as nil

[ThE uSeFuL]

This only works for urls of type "webr.ly" does not work for urls with parameters like youtube.com/watch?v=mqgExtdNMBk

[Vaibhav Saran]

i copied it simply for asp.net regular expression validator ;)

[uɥƃnɐʌuop]

@MrThys - Any chance you could provide examples of which malformed urls this doesn't catch? Would be great to know.. seems an excellent solution so far.

[Aaron Brager]

@DonamiteIsTnt The URL http://www.aol.comhttp://www.nytimes.com passes this test.

[capikaw]

Is there an iOS flavour of this?

[Mike Abdullah]

It should work just fine on iOS. If it doesn't, fix it up and send me a pull request, or file an issue

[denil]

The code will not check for malformed url. Ex: <code>afasd</code>, the url will still pass the test

[newbcoder]

The docs are wrong. Write a few tests — NSURL does not return nil when I pass a string of @"#@#@$##%$#$#", or @"tp:/fdfdfsfdsf". So this method will be useless for checking valid HTTP URLs and the like.

[MuhammadBassio]

perfect, the only problem is that it doesn't recognize www.google.com/+gplusname

[Tony]

If I enter URL like : "file://localhost/...", is it valid?

[Yeung]

((http|https)://)?((\\w)*|([0-9]*)|([-|_])*)+([\\.|/]((\\w)*‌​|([0-9]*)|([-|_])*))‌​+" .It should make http:// or https:// is optiional.

[Revinder]

not working for google.com, www.google.com and also for //www.google.com

[Fattie]

Extremely clever. Real engineering. {You know, I had a weird problem where if I send it the string literally "<null>", it crashes! Could never figure it out.}

[Fattie]

Ah - it was "<null>" in the son, which apple usefully supplies as an NSNull! :O

[bdmontz]

Unfortunately hashtags get turned into NSURLs by this API. As an example "#hashtag" becomes an NSURL.

[Sandy Chapman]

I'm not sure why this has so many upvotes. This method accepts an empty string as a valid URL.

[Yevhen Dubinin]

I created a gist where I started adding test cases for this snipped. Fill free to add more. gist.github.com/b35097bad451c59e23b1.git

[Vincil Bishop]

unfortunately it will return as valid a nil hostname as http://(null)...elegant solution but won't validate even the most basic scenarios.

[Supertecnoboff]

This seems very interesting. Is it 100% bullet proof?

[julianwyz]

I've been using it for a while now and it seems to work fine. It also seems to play nice with the new TLDs (namecheap.com/domains/new-tlds/explore.aspx).

[DJtiwari]

following urls are not working in my case. money.cnn.com/2015/10/19/technology/apple-app-store/…

[newDeveloper]

this seems to work for the test cases @TonyArnold pointed out (iOS 9.1 SDK) but fails for www.microsoft.com because the host is nil. if i do http//www.microsoft.com or http:// microsoft.com, it passes the validation. For an average Joe, www.microsoft.com is a proper url so in my case I've to tweak this solution. Edit: add a ' ' after http:// because SO automatically hyperlinks it.

[Hamza MHIRA]

@DJtiwari +1 yes it's not working did you find any fix for that?

[Legoless]

This is pointless. If your URL is invalid string, it will crash while creating a NSURL, so that could checked instead of this. And even so it uses old API.

[DaNLtR]

@newDeveloper if you add http:// to tp:/fdfdfsfdsf - it passes... check -rocode- answer in the bottom - i think its the best over here.

[Brett]

@Legoless could just use a try...catch around it?

[Krystian]

Not sure where all the upvotes are coming from, but simple check: 123.123.123.123qwe:6001 passes this validation. Quite invalid ;)

[AnLT]

52.88.111.0/API/public/uploads/facilities/images/2585/…. Not working in my case

[zero3nna]

this is not working for more complex url's or fails to get invalid url's like in the comments above shown

[ekashking]

All this goes through: www.ailive wwwailive. I'm not even including com or any extentions.!!! ???????

[Michael]

@Legoless Which version do you work on? This solution works well in my situation.