can't access self? - objective-c

Question

In this function I get xml through a kiss xml function called AFKissXMLRequestOperation. But since it is void, I can't access the XMLDocument unless I NSLog it, but that isn't useful when I need to access the XML. So, I try to set it as a variable of self in order to access it in other functions. If I NSLog self.xmlDocument inside of the block, it works. But, when I NSLog it outside the block in the call NSLog(#"self!%#", [self.xmlDocument XMLStringWithOptions:DDXMLNodePrettyPrint]); it is NULL. So how can I access self.XMLDocument?
-(id)xmlRequest:(NSString *)xmlurl
{
AFKissXMLRequestOperation* operation= [AFKissXMLRequestOperation XMLDocumentRequestOperationWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:xmlurl]] success:^(NSURLRequest *request, NSHTTPURLResponse *response, DDXMLDocument *XMLDocument) {
NSLog(#"kiss operation %#", [XMLDocument XMLStringWithOptions:DDXMLNodePrettyPrint]);
self.xmlDocument=XMLDocument;
} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, DDXMLDocument *XMLDocument) {
NSLog(#"Failure!");
}];
[operation start];
NSLog(#"self!%#", [self.xmlDocument XMLStringWithOptions:DDXMLNodePrettyPrint]);
return self.xmlDocument;
}

Answer 1

NSURLRequest performs asynchroneously, so you will have to review either the way your code is organised, or using a synchroneous network operation.
The error in your above code is that since NSURLRequest performs asynchroneously, the
NSLog(#"self!%#", [self.xmlDocument XMLStringWithOptions:DDXMLNodePrettyPrint]);
return self.xmlDocument;
is performed before the operation has finished, thus returning nil.
Do you really need to return xmlDocument ? I don't think so, because you set it as a property. My guess is that in the success block, (where you set self.xmlDocument=XMLDocument; ) you could actually process the xmlDocument as you want to or call a method that do such.
Hope that helps

Answer 2

I believe AFKissXMLRequestOperation is an asynchronous operation, so you should do what you need to do with the response inside the success block. The success block can certainly call another function if you wish to keep the response handling separate. If you need to pass the response back to another class, you can do that by setting up your own delegate protocol / property or by using blocks yourself:
The delegate protocol:
#protocol XMLResponseHandlerDelegate <NSObject>
- (void)handleResponseXML:(XMLDocument *)xmlDoc;
#end
And then call it:
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:xmlurl]];
AFKissXMLRequestOperation* operation= [AFKissXMLRequestOperation XMLDocumentRequestOperationWithRequest:request
success:^(NSURLRequest *request, NSHTTPURLResponse *response, DDXMLDocument *xmlDocument)
{
NSLog(#"kiss operation %#", [XMLDocument XMLStringWithOptions:DDXMLNodePrettyPrint]);
[self.delegate handleResponseXML:xmlDocument];
}
failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, DDXMLDocument *XMLDocument)
{
NSLog(#"Failure!");
}];