Question

I am learning a lot about memory management but this one problem has me wondering.

In a class method I create a variable:

TBXMLElement *pieceXML = [TBXML childElementNamed:@"piece" 
                                parentElement:rootElement];

And the release it at the end of the method:

[pieceXML release];

But I get the error: Invalid receiver type 'TBXMLElement *'

The implemenation of childElementNamed:parentElement: is below

+ (TBXMLElement*) childElementNamed:(NSString*)aName parentElement:(TBXMLElement*)aParentXMLElement{
    TBXMLElement * xmlElement = aParentXMLElement->firstChild;
    const char * name = [aName cStringUsingEncoding:NSUTF8StringEncoding];
    while (xmlElement) {
        if (strlen(xmlElement->name) == strlen(name) && memcmp(xmlElement->name,name,strlen(name)) == 0) {
            return xmlElement;
        }
        xmlElement = xmlElement->nextSibling;
    }
    return nil;
}

I am trying to understand how I can predict this happening again and any references to reading is welcome since I am not sure how to find the reason for this even after looking.

Thanks.

Answer 1

TBXMLElement is not an Objective-C class — it’s a C struct instead.

This means that pieceXML is not an Objective-C object, hence you cannot send it any Objective-C messages. In particular, you cannot send it -release.