iOS: Strip <img...> from NSString (a html string)

You can use the NSString method stringByReplacingOccurrencesOfString with the NSRegularExpressionSearch option:

NSString *result = [html stringByReplacingOccurrencesOfString:@"<img[^>]*>" withString:@"" options:NSCaseInsensitiveSearch | NSRegularExpressionSearch range:NSMakeRange(0, [html length])];

Or you can also use the replaceMatchesInString method of NSRegularExpression. Thus, assuming you have your html in a NSMutableString *html, you can:

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"<img[^>]*>"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:nil];

[regex replaceMatchesInString:html
                      options:0
                        range:NSMakeRange(0, html.length)
                 withTemplate:@""];

I'd personally lean towards one of these options over the stringByReplacingOccurrencesOfRegex method of RegexKitLite. There's no need to introduce a third-party library for something as simple as this unless there was some other compelling issue.

Use a regular expression, find the matchs in your string and remove them ! Here is how

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"<img[^>]*>"
                                                                       options:NSRegularExpressionCaseInsensitive 
                                                                         error:nil];

NSMutableString* mutableString = [yourStringToStripFrom mutableCopy];
NSInteger offset = 0; // keeps track of range changes in the string due to replacements.
for (NSTextCheckingResult* result in [regex matchesInString:yourStringToStripFrom 
                                                    options:0 
                                                      range:NSMakeRange(0, [yourStringToStripFrom length])]) {

    NSRange resultRange = [result range];   
    resultRange.location += offset; 

    NSString* match = [regex replacementStringForResult:result 
                                               inString:mutableString 
                                                 offset:offset 
                                               template:@"$0"];

    // make the replacement
    [mutableString replaceCharactersInRange:resultRange withString:@""];

    // update the offset based on the replacement
    offset += ([match length] - resultRange.length);
}