handling the singleton object

Question

Sorry to ask basic and some what more important tricky question.I have a singleton class which is already existed in my application( unfortunately i didn't implemented that class).Now i am checking the whole code of the project using the analyzer singleton class showing me the memory leak.I am not sure the code is correct or not because handle singleton class is very tricky.Please any one suggest me why analyzer giving me leak.I attached the singleton class methods please check in the screenshot

In my project we are calling [className sharedDataSource]; many times.Please provide me some knowledge on this Thanks in advance.

Thanks for your response.static KitabooBookListDataSource *_instance = nil; line is there — ajay, Mar 12 '12 at 14:18
Please read: http://cocoasamurai.blogspot.com/2011/04/singletons-your-doing-them-wrong.html — Tim Reddy, Mar 12 '12 at 14:47
Please don't just post screenshots of code; it makes it hard to read. Take a minute to copy-paste. — jscs, Mar 12 '12 at 19:26
Josh Caswell Thanks for your suggestion I follow up for normal scenario.I cant provide you exact problem/information by copy-paste work. — ajay, Mar 13 '12 at 03:25

score 1 · Answer 1 · answered Mar 12 '12 at 14:37

1

I think this is correct. Think about it in terms of what a singleton does. A singleton is a class that lives and there is only a single instance for the entire application. It is a purposeful memory leak. That class is declared and is not supposed be released so that it is available later.

If you use this pattern in objective-c, I think you are responsible for clearing the memory when the singleton is no longer needed.

answered Mar 12 '12 at 14:37

Bill Bonar

1,017
2
10
22

Thanks for your reply I need that singleton instance continuously I cant release it. – ajay Mar 12 '12 at 14:44
Then for clarity i would suggest releasing the singleton when your application exits – Bill Bonar Mar 12 '12 at 14:52

score 1 · Accepted Answer · edited May 23 '17 at 10:30

1

I think its quite safe to ignore that warning really.. For more explanation of how the singleton really behaves as a singleton, you may find this link pretty illuminating.

Long story short, all calls to alloc, in turn call allocwithzone, and in this allocwithzone, there is a condition that makes sure that the alloc happens only once. Agreed, the implementation is quite wonky. However there are quite a few different ways to implement a singleton, as evidenced here, if you feel like refactoring it later or may be even just for academic interest.

edited May 23 '17 at 10:30

Community

1
1

answered Mar 12 '12 at 15:03

govi

687
8
21

I am planning to ignore for the time being. – ajay Mar 12 '12 at 15:39
1

I really don't know why people bother with this horrible pattern. Check out my answer to this question: http://stackoverflow.com/questions/9588253/returning-a-static-with-allocwithzone/9588496#9588496 in particular the GCD version is quite elegant. – JeremyP Mar 12 '12 at 16:54
personally i prefer your second implementation using dispatch_once, this one here feels more like its from java-land – govi Mar 12 '12 at 16:57

handling the singleton object

2 Answers2