Question

Hey everbody. How can i handle a error with the TBXML? I mean, if dont find the file, or what else. Actually, my app just crashes when i turn off the server where the file is.

So, how can i handle that?

- (void)viewDidLoad {

    TBXML * tbxml = [[TBXML tbxmlWithURL:[NSURL URLWithString:@"http://localhost/dev/mcomm/produto.xml"]] retain];
    TBXMLElement * rootXMLElement = tbxml.rootXMLElement;



}

Thanks!

Answer 1

If the error’s coming from the line where you instantiate tbxml you could try wrapping it in a @try/@catch block:

TBXML *tbxml = nil;
@try {
    tbxml = [[TBXML tbxmlWithURL:[NSURL URLWithString:@"http://localhost/dev/mcomm/produto.xml"]] retain];;
}
@catch (NSException *exception) {
    NSLog(@"Caught %@: %@", [exception name], [exception reason]);
}

Alternatively, download the XML data separately using NSURLConnection and use NSURLConnection’s delegate methods to handle error conditions. On success, pass the resulting data to a constructor such as tbxmlWithXMLData:.

EDIT: you’ve commented that the line causing the problem is:

TBXMLElement * xmlElement = aParentXMLElement->firstChild;

The error you’re getting is because you’re trying to dereference a null pointer (aParentXMLElement is nil, and calling ->someMethod on it dereferences it). So all you need there is a guard clause to check aParentXMLElement is non-null before you attempt to dereference it. Something like this:

if (aParentXMLElement != nil) {
    TBXMLElement * xmlElement = aParentXMLElement->firstChild;
} else {
    NSLog(@"Can't proceed: aParentXMLElement is nil");
}