Memory Management Questions

Question

Hello All!
I read the Memory Management Programming Guide for Cocoa - several times. But some things are still not really clear.. I would like and need to have a deeper understanding. So, I hope someone could help me The problem is that I had to get rid of several (..) memory leaks in my app, and now I am a bit confused and unsure about my skills at all..
1.
What is the difference between sayHello1,sayHello2,getHello1,getHello2,getHello3 and which one is "better" (and why) - please dont try to interprete the logic/sense of the methods itself
- (NSString *) sayHello1{
return [[[NSString alloc] initWithString:@"Hello"] autorelease];
- (NSString *) sayHello2{
return [[[NSString alloc] initWithString:@"Hello"] retain];
- (void) getHello1{
NSString *hello = [self sayHello1];
[hello release];
- (void) getHello2{
NSString *hello = [self sayHello2];
[hello release];
- (void) getHello3:(NSString *)hello{
[hello retain];
NSLog(@"%@", hello);
[hello release];
Concerning this, there are several questions:
2.
If I have to release everything I retain/alloc, why then do I have a memory leak, if am returning an object (which was allocated with alloc and init) from a method without autorelease. The object is still in memory. But the following method wont work. What I accept. But the object is, if returned, not reachable, but also not released. Why then is it not automatically released? (i dont mean autorelease)
- (NSString *) sayHello1{
return [[NSString alloc] initWithString:@"Hello"]];
- (void) getHello{
NSString *hello = [self sayHello1]; //wont work. the object is not there, but also not released. WHERE is it?
[hello release];
3.
When is a delegate method released, if I have no variable I can use to "release"? So, if I have nothing to access the delegate like a NSURLConnection delegate?
should I, for example, call a [self release]?
- (void)startParser{
Parser *parser = [[Parser alloc] init];
[parser start];
//should I use a [parser autorelease or retain] here?
- (void)parserDidEndDocument:(NSXMLParser *)parser{
//do somethings with the parserstuff
[self release];
4.
*And the last question:*
Where can I see in instruments, which elements have retain counts > 1 and potential leaks? I was reading the instruments guide but there is only theoretical stuff. No practical guides like: your app should not have/use more than x megabyte ram.. for example: my app gets slower and slower the longer a i use it. -> this indicates memory leaks..

Answer 1

A Leak is only a leak if the reference to the object is lost.
https://devforums.apple.com/message/189661#189661