How to strip down the string? - objective-c

Question

I have a really long string, I just want to extract some certain string inside that string. How can I do that?
for example I have:
this is the image <img src="http://vnexpress.net/Files/Subject/3b/bd/67/6f/chungkhoan-xanhdiem2.jpg"> and it is very beautiful.
and yes now i want to get substring this long string and get only http://vnexpress.net/Files/Subject/3b/bd/67/6f/chungkhoan-xanhdiem2.jpg
Please show me how I can do this.

Answer 1

You can use regular expressions for this:
NSRegularExpression* regex = [[NSRegularExpression alloc] initWithPattern:#"src=\"([^\"]*)\"" options:NSRegularExpressionCaseInsensitive error:nil];
NSString *text = #"this is the image <img src=\"http://vnexpress.net/Files/Subject/3b/bd/67/6f/chungkhoan-xanhdiem2.jpg\"> and it is very beautiful.";
NSArray *imgs = [regex matchesInString:text options:0 range:NSMakeRange(0, [text length])];
if (imgs.count != 0) {
NSTextCheckingResult* r = [imgs objectAtIndex:0];
NSLog(#"%#", [text substringWithRange:[r rangeAtIndex:1]]);
}
This regular expression is the heart of the solution:
src="([^"]*)"
It matches the content of the src attribute, and captures the content between the quotes (note a pair of parentheses). This caption is then retrieved in [r rangeAtIndex:1], and used to extract the part of the string that you are looking for.

Answer 2

You should use a regular expression, probably using the NSRegularExpression class.
Here's an example that does exactly what you want (from here):
- (NSString *)stripOutHttp:(NSString *)httpLine
{
// Setup an NSError object to catch any failures
NSError *error = NULL;
// create the NSRegularExpression object and initialize it with a pattern
// the pattern will match any http or https url, with option case insensitive
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"https?://([-\\w\\.]+)+(:\\d+)?(/([\\w/_\\.]*(\\?\\S+)?)?)?"
options:NSRegularExpressionCaseInsensitive
error:&error];
// create an NSRange object using our regex object for the first match in the string httpline
NSRange rangeOfFirstMatch = [regex rangeOfFirstMatchInString:httpLine
options:0
range:NSMakeRange(0, [httpLine length])];
// check that our NSRange object is not equal to range of NSNotFound
if (!NSEqualRanges(rangeOfFirstMatch, NSMakeRange(NSNotFound, 0)))
{
// Since we know that we found a match, get the substring from the parent
// string by using our NSRange object
NSString *substringForFirstMatch = [httpLine substringWithRange:rangeOfFirstMatch];
NSLog(#"Extracted URL: %#",substringForFirstMatch);
// return the matching string
return substringForFirstMatch;
}
return NULL;
}

Answer 3

NSString *urlString = nil;
NSString *htmlString = //Your string;
NSScanner *scanner = [NSScanner scannerWithString:htmlString];
[scanner scanUpToString:#"<img" intoString:nil];
if (![scanner isAtEnd]) {
[scanner scanUpToString:#"http" intoString:nil];
NSCharacterSet *charset = [NSCharacterSet characterSetWithCharactersInString:#">"];
[scanner scanUpToCharactersFromSet:charset intoString:&urlString];
}
NSLog(#"%#", urlString);