I have a question about Storyboard, Segues and memory management. If I read about it on forums people say this is working properly but I was wondering the following, I made a small video to illustrate:
https://www.youtube.com/watch?v=ixs1Fiv5M9s
I grabbed a source from github explaining segues and unwinding them
I tested this in debugging and indeed I see all functions including dealloc is working
I run instruments and check how many times 2de view controller is created (every time #Persistent is increasing)
I check for changes in memory between the 2 states, and a lot is still in memory? But View controller is gone?
I am looking for the wrong data in instruments? I guess looking for memory leaks using modal and dismissing a view controller is not the right way to do this?
Can somebody explain me how to look for memory leaks? I need this for a much bigger app that is using a lot of segues, and sometimes this app crashes because of memory warnings...
Related
I'm having a memory issue with one specific ViewController and memory. When I launch my app in debug mode, it launches with 40mb memory usage. (I have no idea if this is already a lot or not -- what is common?). Then, when I open this specific view, it spikes up to about 120mb. The issue is, when I pop this view (with the navigationController popViewController), the memory stays up at 120mb. And then, when I re-open it, it spikes to 200mb (a 80mb increase every time).
With other similar ViewController it spikes up to 120mb too, but when I close the view, it goes back down to more or less 40mb.
The problem is that this specific view contains quite a bit of code (about 1000 lines...) and it's impossible for me to post everything here.
What methods should I use to specifically locate the issue in xCode?
For anyone I might be able to help with this:
use the tools in xCode as recommended. There are some great tutorials online.
In my case it was an issue with an [NSTimer] which kept a strong reference to my view, so it never got released afterwards, thus stacking up memory. Make sure to stop your time when you pop a view.
I am writing my whole app from code and i am not using storyboard.But My app is using much memory. I have some view controller,TableViewController, collectionView and some webview in my apps.
And I am pushing all viewController and instantiating navigationViewController from RootviewController to it's childviewController.
And I am think that the ARC is not working is enable in my project.And When the memory reaches maximum my app is kill by iPhone.
wow, that's a lot of memory!
I don't have much experience with webviews, but I might be able to help with the other components.
As a suggestion: Make use of the debugger to go through your code step by step and keep an eye on the memory inside XCode.
You might be able to find out which part of your code generates so much memory usage that way.
If you can't find the problem: It is very hard to tell where this effect comes from. It might be a little easier if your post your code (preferably commented) so we can dig deeper into what might be causing this problem.
Cheers,
Ferdinand
check if there are any memory retain cycles, when refrencing self inside closure always use weak reference.
I am going in and out of UIViewControllers.
Every time I am going in memory increases, but when I am getting out (pressing Back) memory is not decreasing.
I have weak #IBOutlets, vars and lets.
How can I fix it?
p.s. One of the #IBOutlet is container pointing to another UIViewController
Ignore the comments suggesting retain/release breakpoints and peppering your code with log calls; that's an unwieldy tactic that misses entire classes of problems. Abizern's suggestion to use Instruments is a lot more spot-on. Run the Leaks instrument to look for leaked instances. Browse the other memory instruments as well. Instruments is a &#&$&-ing magical debugging tool and so many developers ignore it for reasons I can't fathom. Spend a few minutes with a tutorial and you'll save months of debugging time over your career.
It sounds like you are creating a new UIViewController every time you switch between views. Try to create the segue to be an unwind segue, this will remove the current view from the stack. Otherwise it appears that you are just continually adding to the stack of views. Tell me if this works.
I am quite beginner in development and I'm making an application that have about 150 ViewControllers ! Each one have a UIImageView.
I've been doing a bit of testing, and after a use the app for a while on the iPhone itself, it Crashes when I keep viewing the ViewControllers.
I've been analyzing this in instruments, and I have no leaks, however my memory allocation just goes up and up and when I keep viewing the ViewControllers on my iPhone the usage just goes up and up until a crash.
I think it's clear that it's crashing because the app is simply taking up too much memory.
So could any one explain how to release viewControllers in order to free up the memory so there will be no crash
Thanks in advance !
The first question you need to ask yourself is why do you need 150 ViewControllers.
Do you want to present 150 different images?
If so, then multiple ViewControllers is not the way to go. You probably need to use a UIScrollView that will contain your images (not all of them at once, of course. Use lazy loading).
What's probably happening in your case is that you call "pushViewController" each time you need to display a new ViewController, but this doesn't release the previous ViewController. It simply stacks all of the previous ViewControllers and retains their pointers.
You see, the way Navigation Controllers work is that they have an array of view controllers. Every time you present a new view controller, it is added at the end of the array. When you click on "Back" or call "popViewController" the last item of the array is removed (and then released automatically from memory).
See this and this questions to learn how to create a UIScrollView to scroll images.
I just started learning the instruments tool, and I'm pretty sure what I am seeing is not good. When I look at allocations, specifically the column "Live Bytes" and "Overall Bytes", I see the number continually increases as the app runs...
My app has two view controllers. A table view, and the second view controller displays detailed information about the row they selected in the table view, downloaded from the internet.
I kept clicking a row in the table view, followed by clicking the back button in the navigation bar... and LiveBytes continued to increase.
I'm guessing this means that my objects aren't being released from memory... but please correct me if I'm wrong.
MY QUESTION IS: How do I use the data in instruments/allocations to track down this memory issue? How do I find the objects not being released from memory?
I'm looking for tips on how to use these tools to clean up any memory problems my app has.
Thanks!
XCODE 4.2.1, deploying to iOS 5.0+
EDIT: I'm looking at the #living column and seeing objects like UIScrollView continuously increase... and never decrease. When I click the back button in a navigation bar, are objects automatically released from memory? When are objects released, or do I need to do it manually? Or could I be running into an issue due to using strong pointers, causing objects to not be released?
Whenever you want to observe memory usage in a cyclic pattern, there's the wonderful Heapshot analysis in the "Allocations" instrument.
Start your app and go to a default state.
In Instruments, press the "Mark Heap" button to create the "Baseline".
Do something in your app like pushing a view controller.
Return to the default state.
Press the "Mark Heap" button again to create a heapshot.
Repeat about five times from step 3.
This will result in a list of heapshots, each showing the objects that are still alive from that cycle. If your app has no leaks there will be no objects left in the middle heapshots.
The first one or two cycles might have warmed up some caches, the last two might not have cleaned up some reused resources. That's why it's usually a good idea to make four to six heapshots.
The magic in the heapshot analysis lies in the fact that the heapshots show you the leaked objects from previous cycles and remove them automatically when the objects are released later. In contrary to the "Leaks" instrument it also finds abandoned memory, not only leaks.
Most Probably you have discarded the arm64 and are running your app with armv7 only. Add both arm64 and armv7 as architectures
I think one of the best ways to solve memory issues is to use ARC.
Edit -> Refactor -> Upgrade to Objective-C ARC.
ARC will handle the majority of memory management in your app. Especially sice your app doesn't sound too complex, it might totally eliminate your problem. You still need to watch out for retain cycles and listen to memory warnings though. If you don't want to use ARC (which you should) at least run the static analyzer. Your problem might be something simple that the static analyzer can show you how to fix.
Edit:
You mentioned scroll views- this might be your problem: Memory leak every time UIScrollView is released
The profile tool has an instrument called 'Leaks'. It is similar to the 'Allocations' instrument but it shows you the object that was not released. May be you can use the 'Leaks' tool to find what is the object that was retained and release these object.