What increases an object’s retain count?

by

You are correct that the retain count is 2 after adding it to an array. However, you should only worry about the retain counts you add to the item explicitly.

Retaining an object is a contract that says “I’m not done with you, don’t go away.” A basic rule of thumb (there are exceptions, but they are usually documented) is that you own the object when you alloc an object, or create a copy. This means you’re given the object with a retain count of 1(not autoreleased). In those two cases, you should release it when you are done. Additionally, if you ever explicitly retain an object, you must release it.

So, to be specific to your example, when you create the Person, you have one retain count on it. You add it to an array (which does whatever with it, you don’t care) and then you’re done with the Person, so you release it:

Person *p = [[Person alloc] init]; //retain 1, for you
[array addObject:p]; //array deals with p however it wants
[p release]; //you're done, so release it

Also, as I said above, you only own the object during alloc or copy generally, so to be consistent with that on the other side of things, you should return the array autoreleased, so that the caller of the getPeople method does not own it.

return [array autorelease];

Edit:
Correct, if you create it, you must release it. If you invest interest in it (through retain) you must release it.

More Related Contents:

  1. When to use -retainCount?
  2. Why is @autoreleasepool still needed with ARC?
  3. Retain cycle on `self` with blocks
  4. Why would you use an ivar?
  5. Class methods which create new instances
  6. How does the NSAutoreleasePool autorelease pool work?
  7. When to access properties with ‘self’
  8. Weak NSString variable is not nil after setting the only strong reference to nil
  9. capturing self strongly in this block is likely to lead to a retain cycle
  10. In which situations do we need to write the __autoreleasing ownership qualifier under ARC?
  11. @property definitions with ARC: strong or retain?
  12. Memory Management in Objective-C [duplicate]
  13. Why has NSNumber such strange retainCounts?
  14. How is release handled for @synthesized retain properties?
  15. With ARC, what’s better: alloc or autorelease initializers?
  16. Tagged pointers in Objective-C
  17. What is the cost of using autorelease in Cocoa?
  18. Does @”some text” give an autoreleased or retain 1 object back?
  19. What is the difference between a __weak and a __block reference?
  20. Best way to define private methods for a class in Objective-C
  21. Are Swift variables atomic?
  22. How to detect if NSString is null?
  23. Shift hue of an RGB Color
  24. Correct crop of CIGaussianBlur
  25. NSTask not picking up $PATH from the user’s environment
  26. Cocoa/Objective-C : Best Practice to parse XML Document?
  27. UIWebView iOS5 changing user-agent
  28. Getting a random object from NSArray without duplication
  29. Finding file’s size
  30. dispatch_sync on main queue hangs in unit test

Leave a Comment