iOS : How to do proper URL encoding?

Question

I'm unable to open a URL into UIWebView so I've seached & found that I need to encode URL, so I tried to encode it but, I've facing problem in URL encoding : My URL is http://somedomain.com/data/Témp%20Page%20-%20Open.html (It's not real URL).

I'm concerned with %20 that I tried to replace using stringByReplacingOccuranceOfString:@"" withString:@"" , it give me the URL I wanted like http://somedomain.com/data/Témp Page - Open.html However its not opening in UIWebView but amazingly it opens in Safari & FireFox perfect. Even I open unencoded URL its automatically converts and open the page I'm looking for.

I've google for URL encoding & it points me to different results I already checked but no results help me out!! I tried different functions answers in different URL encoding question but it just changed all special characters and make my URL like, http%3A%2F%2Fsomedomain.com%2Fdata%2FT... which can't open in UIWebView and even in any browser.

It gives the following Error Log in UIWebView delegate

- (void)webView:(UIWebView *)webView didFailLoadWithError:(NSError *)error { }

Error Code : 101 & Description : Error Domain=WebKitErrorDomain Code=101 "The operation couldn’t be completed. (WebKitErrorDomain error 101.)" UserInfo=0x6e4cf60 {}

Answer 1

The answer @Dhaval Vaishnani provided is only partially correct. This method treats the ?, = and & characters as not to be encoded, since they're valid in an URL. Thus, to encode an arbitrary string to be safely used as a part of an URL, you can't use this method. Instead you have to fall back to using CoreFoundation and CFURLRef:

NSString *unsafeString = @"this &string= confuses ? the InTeRwEbZ";
CFStringRef safeString = CFURLCreateStringByAddingPercentEscapes (
    NULL,
    (CFStringRef)unsafeString,
    NULL,
    CFSTR("/%&=?$#+-~@<>|\\*,.()[]{}^!"),
    kCFStringEncodingUTF8
);

Don't forget to dispose of the ownership of the resulting string using CFRelease(safeString);.

Also, it seems that despite the title, OP is looking for decoding and not encoding a string. CFURLRef has another, similar function call to be used for that:

NSString *escapedString = @"%32%65BCDEFGH";
CFStringRef unescapedString = CFURLCreateStringByReplacingPercentEscapesUsingEncoding (
    NULL,
    (CFStringRef)escapedString,
    CFSTR(""),
    kCFStringEncodingUTF8
);

Again, don't forget proper memory management.