Question

I use this code to retrive the first image of a feed…
the htmlString contains html tags and in same cases I can get correctly the first image but in other cases i get a nil NSString. I don’t understand why. I’m sure that the htmlString contains one image. For example for this String I can’t get correctly the first image.

Example:
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The part of code that I need is: <img class="aligncenter size-full wp-image-21789" title="mac-app-store_t" src="http://static.slidetomac.com/wp-content/uploads/2011/07/mac-app-store_t.jpg" alt="" width="507" height="300" /

But I can’t get correctly the url of the image…
What’s wrong in my code?
thanks

- (NSString *)getFirstImage:(NSString *)htmlString{



    NSString *urlImage=nil;
    NSScanner *theScanner = [NSScanner scannerWithString:htmlString];
    // find start of IMG tag
    [theScanner scanUpToString:@"<img" intoString:nil];
    do {
        [theScanner scanUpToString:@"src" intoString:nil];
        NSCharacterSet *charset = [NSCharacterSet characterSetWithCharactersInString:@"\"'"];
        [theScanner scanUpToCharactersFromSet:charset intoString:nil];
        [theScanner scanCharactersFromSet:charset intoString:nil];
        [theScanner scanUpToCharactersFromSet:charset intoString:&urlImage];

        if([urlImage rangeOfString:@"imagebutton.gif"].location == NSNotFound) return urlImage;


    }while (![theScanner isAtEnd]  );


    if([theScanner isAtEnd]) return nil;
     return urlImage;
}

Answer 1

What’s wrong in my code?

You are using a scanning parser to parse HTML.

HTML parsing is very very hard; all of the problems of an XML parser combined with a pervasive lack of consistency.

Fortunately, HTML parsing is also very much a solved problem.

Use a proper HTML Parser. libxml2 has an HTML compliant mode.

There are a slew of question/answers on SO about HTML parsing.