Application start debuging at pool drain instruction - iphone

Question

I am build an iPhone application who try to perform a login via a Rest web service (WCF).
The part who call the service work correctly. I receive data from the called service without any problem.
But I have to parse the message using the NSXMLParser. When I introduce it in my application (this is the first time I used it) the application parse the message correctly but at the end of the application execution it's lunch gdb and pause the application at the start of [pool drain] instruction.
#interface MessageParser : NSObject <NSXMLParserDelegate> {
NSMutableString* currentProperty;
Message* message;
}
#property (nonatomic, retain) NSMutableString* currentProperty;
#property (nonatomic, retain) Message* message;
- (void)parseMessageData:(NSData *)data parseError:(NSError **)err;
#end
#implementation MessageParser
#synthesize message, currentProperty;
- (void)parseMessageData:(NSData *)data parseError:(NSError **)err {
NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
[parser setDelegate:self];
[parser setShouldProcessNamespaces:NO];
[parser setShouldReportNamespacePrefixes:NO];
[parser setShouldResolveExternalEntities:NO];
[parser parse];
if (err && [parser parserError]) {
*err = [parser parserError];
}
[parser release];
}
-(void) parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{
if(qName){
elementName = qName;
}
if([elementName isEqualToString:#"Message"]){
self.message = [[Message alloc] init];
}
else if( [elementName isEqualToString:#"body"] || [elementName isEqualToString:#"code"] || [elementName isEqualToString:#"error"]){
currentProperty = [NSMutableString string];
}
}
-(void) parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
if(qName){
elementName = qName;
}
if(message){
if([elementName isEqualToString:#"body"]){
self.message.messageBody = currentProperty;
}
else if([elementName isEqualToString:#"error"]){
self.message.error = currentProperty;
}
else if([elementName isEqualToString:#"code"]){
NSNumberFormatter * f = [[NSNumberFormatter alloc] init];
[f setNumberStyle:NSNumberFormatterDecimalStyle];
self.message.messageCode = [f numberFromString:currentProperty];
[f release];
}
}
self.currentProperty = nil;
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)foundedCharacters
{
if (self.currentProperty) {
[currentProperty appendFormat:#"%#", foundedCharacters];
}
}
Some time the debugger give me this message : Attempting to create USE_BLOCK_IN_FRAME variable with block that isn't in the frame.
Do you have any idea ?
Thank you.

Answer 1

This can be done using method swizzling:
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#interface NSAutoreleasePool(customDrain)
-(void) myDrain;
#end
#implementation NSAutoreleasePool(customDrain)
-(void) myDrain
{
if ([self respondsToSelector:#selector(myDrain)])
{
NSLog(#"Draining...");
// note that #selector(myDrain) was remapped
// to #selector(drain) during the process of
// the swizzling, so now, myDrain calls drain,
// and drain calls myDrain.
[self myDrain];
}
else
{
NSLog(#"Remapping Failed!");
}
}
#end
void SwizzleMethod(Class c, SEL orig, SEL new);
void SwizzleMethod(Class c, SEL orig, SEL new) {
Method origMethod = class_getInstanceMethod(c, orig);
Method newMethod = class_getInstanceMethod(c, new);
if (origMethod && newMethod)
method_exchangeImplementations(origMethod, newMethod);
}
int main (int argc, const char * argv[])
{
NSAutoreleasePool *pool = [NSAutoreleasePool new];
SwizzleMethod([NSAutoreleasePool class], #selector(drain), #selector(myDrain));
[pool drain];
return 0;
}
You simply put your own code in the category's myDrain method, and, then, you run your own code when the pool is drained.
I hope this helped.