The main difference is that you can send messages to nil , so you can use it in some places where null cant work. The effect of a further method calls through this pointer is one of these three which one is undefined :.
Now the object reference is nil and any further method calls are ignored. This may silently cause a defined but unforeseen lateral effect in your code, but at least it doesn't crash your application. This is the same as before, but it removes that small window between release and nil where the object reference points to an invalid object.
A easy way to defer your choice is using a macro. Instead [airplane release] you write safeRelease x where safeRelease is the following macro that you add to your.
This macro doesn't respect zombies. If you nil its object reference, any call sent to him will be ignored. This guarantees a crash during debug time if zombies are not enabled, but leaves the zombies be otherwise. Apple doesn't have a recommendation on which one is best.
If you open the nib file in interface builder you will see a proxy icon that represents the owner of the nib file. You can make connections to it but the connections are not established UNTIL the nib file is loaded and you specify who the onwer really is.
Anyways, you can have an outlet e. When you load the nib file and specify the owner that i-var will now point to the UI object. Let's say it is a window. Eventually when you decide to get rid of the UI objects you simply release the owner and if it reaches a retain count of zero the dealloc method will get called. Then the dealloc method in the owner should release it's i-vars instance variables. So let's say the i-var that you connected to the window is called window.
Then you should have something like this:. That should then cause the window to reach a count of zero. Then the window's dealloc should get called and it will subsequently release all the retains on the subviews, and the subviews will reach a retain count of zero and they will subsequently release all the retains on their subviews, and so on until everything is dealloced.
There's an application from Omni called OmniObjectAlloc or something like that which should be very helpful in looking at your app and figuring out if everything is getting dealloced. Look for it, I would imagine it's still there. Its based on the scope of the object that you actually create or retain. Whenever the retaincount is brought back to 1, dealloc method will be called by its own. For a managed C object to be eligible for collection it must be referenced from no managed root and also from no native root represented by a GCHandle object.
If no such handle exists, and no reference from a managed root exists, the managed object becomes eligible for collection. In general you should not use finalizers often, if at all. They are for cleaning up unmanaged resources. You can also read more about finalizers and IDisposable here.
All NSObjects use this to coordinate between the native object and the managed wrapper. The articles that have been posted here have been helpful, and I have made the following assumptions. I have been having problems understanding memory issues, and the profiler xamarin and instruments don't seem to be consistence and are confusing me.
I believe this is true, but keep in mind that GC is not the same as finalization. The GC finds objects that are candidates for collection, but any of those that have finalizers will not be collected at that time.
Instead, they go on the finalizer queue, which keeps the object alive until the finalizer runs. The runtime typically and definitely in the case of mono has its own thread where it runs the finalizer. That thread pulls objects off the queue as it can, and only once that object has had its finalizer run does it again become a candidate for collection.
Therefore when an object has a finalizer it has to go through the GC twice. That Dispose and finalizer will always be called when the object get collected; unless finalizer is suppressed CG. SuppressFinalize object. This isn't quite right. First, the GC doesn't by itself know anything about Dispose. So objects inside them will be never deallocated too.
Maybe I am living in a strange world.. So please help me understand the fault in my thinking and expectations. An object by definition is an association of code and data. In many cases your code in a class instance allocates resources other than memory.. These methods would have to be explicitly called by the caller.. It would be the same trouble as we have we -dealloc at the moment. This I have done.. Seems to work..
This is weird to me.. Since I must explicitly be on guard.. But not as a normal case.. It should never be purposely violated.. Only an unmanagable expection should create this trouble.. Terminating an application is not normally considered an unmanagable exception case.
Everyone is forced to first understand the fault, and then work-around it. Are you really willing to trade potential system leaks for a few millisecs gain on the death of an app or a thread? Maybe I am a victim of my upbringing.. When system resources were expensive, and memory was sparse.. So, If I am the only person in the world that thinks the Cocoa behaviour is strange.. Then I am doomed to be lonely in my old-age..
I think I can help. Consider the way that objects in Objective-C are created. First you call -alloc to allocate some memory for your new object, and then you call -init or some variant of -init to initialize your object. If you have code in your application which is misbehaving then you lose, period.
The question is how you ensure that these leaks do not occur. In Cocoa this is not the case. They are merely different techniques. The documentation for runFinalizersOnExit states:. This method is inherently unsafe. It may result in finalizers being called on live objects while other threads are concurrently manipulating those objects, resulting in erratic behavior or deadlock.
Therefore your statements about garbage collection are not correct for all systems. I would not be surprised if other GC systems were the same. A terminating application cannot leak memory, file handles, sockets, or non-distributed locks. In any case, anything which the OS cannot clean up will not be cleaned up if your application should crash, so the possibility of a leak is always there. I have for years worked in both the PC and embedded worlds.
I have never embraced Java, due mostly to performance issues.. I have had to be responsible to take out my own trash. My work has been focused mainly in high-speed vision systems and optimization lines for the solid wood industry. So to me it is natural to expect that this is a basic premise..
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