Tuesday, August 14, 2012

How to use NSScanner on NSString.

This is quiet useful in terms of parsing a simple static webpage, also pick certain kind of words from the NSString.

Lets say we have following snippet from a html file.


NSString *htmlString=


< div id="topLeft" class="news" style="padding-top:3px"
onMouseOver="style.color='white';style.backgroundColor='#F0ABFF'" onMouseOut="style.color='black';style.backgroundColor='#000000'"><style="text-decoration:none;color:black" onMouseOver="style.color='white'" onMouseOut="style.color='black'"href="reetu/test/news.htm" target="_blank">Latest News</a>


Now I want to extract the url, text and div id from this html file snippet. Following code will give you that.


     NSScanner *rScanner = [NSScanner scannerWithString:string];
     NSString *divID=@"";
    [rScanner scanString:@"<div id=\"" intoString:NULL];
    [rScanner scanUpToString:@"class=\"news\"" intoString:&courseID];

     divID=[divID stringByReplacingOccurrencesOfString:@" " withString:@""];
     divID=[divID stringByReplacingOccurrencesOfString:@"\"" withString:@""]; 
     divID=[divID stringByReplacingOccurrencesOfString:@"<divid=" withString:@""]; 
     NSLog(@"divID=%@",divID);           

/*Instead of above 3 lines you could also do [rScanner scanUpToString: instead of scanString:
    

    NSString *rURL=@"";
    [rScanner scanUpToString:@"href=\"" intoString:NULL];
    [rScanner scanUpToString:@">" intoString:&rURL];
     rURL=[rURL stringByReplacingOccurrencesOfString:@"href=\"" withString:@""];
     rURL=[rURL stringByReplacingOccurrencesOfString:@"target=\"_blank\"" withString:@""];
     rURL=[rURL stringByReplacingOccurrencesOfString:@"\" " withString:@""];
     NSLog(@"rURL=%@",rURL);






   NSString *rName=@"";
   [rScanner scanUpToString:@"</a>" intoString:&rName];
    rName=[courseName stringByReplacingOccurrencesOfString:@">" withString:@""];
    NSLog(@"rName=%@",rName);
    

    


    




It will print following results:


divID=topLeft
rURL=reetu/test/news.htm
rName=Latest News



Read More: https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/Strings/Articles/Scanners.html


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