I am learning the course CS193P(IOS develop) on itunes and I just started assignment2. I got stuck on the task that asks me to restart the game.
A little bit background on the project: I am writing code for the newly added action method for the restart button in my CardGameViewController. I have two private properties: game and deck. I use lazy initialization in the CardGameViewController to initialize them when user first touch a button(flip a card).(The original project that the professor went over in the lecture is just some cards on the UI and user can flip them around and match them,without the restart function, which is the one I am asked to add in the homework.)
In order for the user to restart the game, I think I need to reinitialize the two properties I mentioned above and update the UI. I tried the following code but the program crashed when I touch the button I just added:
- (IBAction)touchRestartButton:(UIButton *)sender
{
self.game = nil;
self.theDeck = nil;
// Maybe I also need to initialize the two properties again here using some code which I cannot figure out right now....
[self updateUI];
}
Can anyone explain to me how to reinitialize a property in objective-c?(I also tried [self.game release], but the complier prevented me to do this because it says it is in ARC mode)
Or is there any other way to finish this restarting game task?
Related
I wondered if anyone could provide advice on how I can ‘force’ the UI to update during a particularly intensive function (on the main thread) in Swift.
To explain: I am trying to add an ‘import’ feature to my app, which would allow a user to import items from a backup file (could be anything from 1 - 1,000,000 records, say, depending on the size of their backup) which get saved to the app’s CodeData database. This function uses a ‘for in’ loop (to cycle through each record in the backup file), and with each ‘for’ in that loop, the function sends a message to a delegate (a ViewController) to update its UIProgressBar with the progress so the user can see the live progress on the screen. I would normally try to send this intensive function to a background thread, and separately update the UI on the main thread… but this isn't an option because creating those items in the CoreData context has to be done on the main thread (according to Swift’s errors/crashes when I initially tried to do it on a background thread), and I think this therefore is causing the UI to ‘freeze’ and not update live on screen.
A simplified version of the code would be:
class CoreDataManager {
var delegate: ProgressProtocol?
// (dummy) backup file array for purpose of this example, which could contain 100,000's of items
let backUp = [BackUpItem]()
// intensive function containing 'for in' loop
func processBackUpAndSaveData() {
let totalItems: Float = Float(backUp.count)
var step: Float = 0
for backUpItem in backUp {
// calculate Progress and tell delegate to update the UIProgressView
step += 1
let calculatedProgress = step / totalItems
delegate?.updateProgressBar(progress: calculatedProgress)
// Create the item in CoreData context (which must be done on main thread)
let savedItem = (context: context)
}
// loop is complete, so save the CoreData context
try! context.save()
}
}
// Meanwhile... in the delegate (ViewController) which updates the UIProgressView
class ViewController: UIViewController, ProgressProtocol {
let progressBar = UIProgressView()
// Delegate function which updates the progress bar
func updateProgressBar(progress: Float) {
// Print statement, which shows up correctly in the console during the intensive task
print("Progress being updated to \(progress)")
// Update to the progressBar is instructed, but isn't reflected on the simulator
progressBar.setProgress(progress, animated: false)
}
}
One important thing to note: the print statement in the above code runs fine / as expected, i.e. throughout the long ‘for in’ loop (which could take a minute or two), the console continuously shows all the print statements (showing the increasing progress values), so I know that the delegate ‘updateProgressBar’ function is definitely firing correctly, but the Progress Bar on the screen itself simply isn’t updating / doesn’t change… and I’m assuming it’s because the UI is frozen and hasn’t got ‘time’ (for want of a better word) to reflect the updated progress given the intensity of the main function running.
I am relatively new to coding, so apologies in advance if I ask for clarification on any responses as much of this is new to me. In case it is relevant, I am using Storyboards (as opposed to SwiftUI).
Just really looking for any advice / tips on whether there are any (relatively easy) routes to resolve this and essentially 'force' the UI to update during this intensive task.
You say "...Just really looking for any advice / tips on whether there are any (relatively easy) routes to resolve this and essentially 'force' the UI to update during this intensive task."
No. If you do time-consuming work synchronously on the main thread, you block the main thread, and UI updates will not take effect until your code returns.
You need to figure out how to run your code on a background thread. I haven't worked with CoreData in quite a while. I know it's possible to do CoreData queries on a background thread, but I no longer remember the details. That's what you're going to need to do.
As to your comment about print statements, that makes sense. The Xcode console is separate from your app's run loop, and is able to display output even if your code doesn't return. The app UI can't do that however.
So I've been developing with a company's private SDK recently, and basically their SDK acts as another "input" form for the user. I'm using SpriteKit and their SDK (for the input) to make a game, but there's one last bug preventing me from finishing.
The event-triggered method (called every time input occurs) just stops being called at random times, even when there is valid input. I don't think the fault is with the SDK, since I've seen many examples of it working fine. I've ran the allocation instrument during debugging, and the bug occurs even when no major allocations are occurring. I'm posting here to ask for advice not necessarily on how to fix the bug, but on how to debug it, since obviously not much information about the SDK can be given here.
This might be a problem with SpriteKit and/or how I'm using SpriteKite. Any help/advice is much appreciated.
Also please comment if you need more information. I'm very confused about this bug so I don't know what other information I could give that'd be useful.
MyScene.h
#interface MCGMyScene : SKScene <sdkDelegate, UIAccelerometerDelegate>
//properties and methods...
#end
MyScene.m
- (id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
//initialization...
//set "self as the delegate for the SDK
}
return self;
}
// This method is triggered purely by the SDK, whenever it registers input
- (void)SDKInputUpdate:(int)x
{
[player updatePlayerWithInput:x];
// for debugging I've put in basic code here to track when the method stops being called
}
Thanks
Hi in my application i have two types of syncs. 1.Auto sync 2.Manual Sync. In both the syncs i am downloding a bunch of files from server. If I choose auto sync all files will get download.
Code is like this
for(int i=0;i<filescount;i++)
{
[self downloadfiles];
}
-(void)download files
{
//Here i am creating `NSInvocationOperation`.
if(!synchingfilecount)
totalreceiveddata=0;
}
Based on totalreceiveddata I am updating progress bar. Now the issue is if it autosync it is working fine.While downloading files using autosync and in middle if i click manual sync that time [self downloadfiles]; method will get called but the issue is synchingfilescount is not updating immediately it's completeing the autosyncfiles download and synchingfilescount become 0 due to this reason totalreceiveddata become 0 and progress bar is disappearing. After complete this opertiona again synchingfilecount becomes 4 but i cannot able to see the progress bar due to above situation. Please any one help me how can I come out from this situation.
Ok, if I understand your question correctly, it sounds like you need to create some flags so that you can manage the flow of your code. You can do this by making a boolean property and setting it as you need in the completion block of these sync methods. That way you can call a method or only execute a method after the call is complete.
I have a view with a bunch of UISwitch.
My problem is that when I tap on a switch I need to wait about 10 seconds before being able to tap any other switch of the view.
Here is my code :
-(void) didTapSwitch:(UISwitch *)sender
{
NSLog(#"BEGIN didTapSwitch, %#",sender);
DADudesManager *dudesManager = [DADudesManager getInstance];
DADude *updatedDude = [dudesManager.dudesList objectAtIndex:[[self.spendingDudesTableView indexPathForCell:sender.superview.superview] row]];
DAAccountManager *accountManager = [DAAccountManager getInstance];
[accountManager.accountsOperationQueue addOperationWithBlock:^{
NSLog(#"BACKGROUND OPERATION BEGINS switchDudeBeneficiates, %#",sender);
DASpendingsManager *spendingsManager = [DASpendingsManager getInstance];
[[spendingsManager.spendingObserver childByAppendingPath:self.spending.spendingID] updateChildValues:#{updatedDude.dudeName: [sender isOn] ? #"1" : #"0"}];
NSLog(#"BACKGROUND OPERATION ENDS switchDudeBeneficiates, %#",sender);
}];
NSLog(#"END switchDudeBeneficiates, %#",sender);
}
My spendingObserver is a Firebase object initiated before.
When the code above is executed, the NSLogs show almost instantaneously in the console, the data is updated online at the same time, but the switches don't react to any tap for another 9 to 11 secs.
Of course commenting the line [[spendingsManager.spendingObserver childByAppendingPath:self.spending.spendingID] updateChildValues:#{weakDude.dudeName: [weakSwitch isOn] ? #"1" : #"0"}]; removes the latency, so the problem must come from Firebase, but I have no clue what's going on.
I am probably missing something obvious as I'm pretty new to IOS development !
I can think couple of reasons.
You are sending the PayLoad in the main thread, which is causing the User INterface events to be suspended.
The code you ran, might be linked to other functions in the library you are using, that might be causing the lag.
TRY - >
try putting your code in an NSOperation and execute that. Or use GCD to do work on different thread just not the UI thread which is the main thead.
Step back and simplify. Make your switch code simply log the change in value. NSLog includes a timestamp, so you can tell when the switch events occur.
If do-nothing code responds quickly, as I suspect it will, then add log statements at the beginning and end of your switch action method. That way you can see if there is a delay between the beginning and end of the processing.
You could also run the app in instruments (time profiler) and see where your app is spending time.
I get a strange crash when using the new PageCurl effect reading a PDF with MonoTouch and iOS 5.0.
I've made a simple test case project for MonoDevelop 2.8 and uploaded on GitHub here:
https://github.com/Emasoft/IpaziaPDFReader
It seems that something is getting GCd too early and killing the application, but I can't find what. I've tried to dispose everything in many ways, but in vain. I've already submitted the project tarball to the Xamarin team, but they weren't able to solve the problem.
Is there something broken in the iOS NavigationController memory management? Or am I missing something?
Any help is appreciated, thanks!
UPDATE: I've tried to remove all subviews and sublayers before disposing the objects in all classes, but it still crashing. The only way I found to avoid the crash is to NEVER dispose of the PDF pages, adding them to a List before releasing them, but this is not a viable solution, because in that way memory is consumed rapidly for PDF with many pages and the app crashes anyway when unable to allocate memory for the next page.
Another way to avoid the crashes is to dispose of the PDF pages BEFORE turning the pages, forcing the dispose method on the page controller before creating a new page controller, but in this way the current page will become blank and the transition curls an useless empty page. No solution seems to work.
I've updated project on GitHub with the 3 different solutions I've tried (look in the PageDataSource class), you can uncomment them one at time to see the problems.
//SOLUTION 1
void ForcingPageControllerDispose (BookPageController oldPageController)
{
// --- IF YOU UNCOMMENT THIS, THE CRASHES GO AWAY, BUT THE PAGE IN THE TRANSITION IS BLANK, SO IS NOT VIABLE
currentPageController.View.RemoveFromSuperview ();
currentPageController.Dispose ();
}
//SOLUTION 2
void DisposeThePageControllerWhenDidFinishAnimating (BookPageController oldPageController, UIPageViewController pageViewController)
{
// --- IF YOU UNCOMMENT THIS, THE CRASHES STILL HAPPEN
pageViewController.DidFinishAnimating += delegate(object sender, UIPageViewFinishedAnimationEventArgs e) {
if (currentPageController != null) {
currentPageController.View.RemoveFromSuperview ();
currentPageController.Dispose ();
Console.WriteLine ("currentPageController disposed for page: " + currentPageController.PageIndex);
}
};
}
//SOLUTION 3
void BackupUnusedPagesToAvoidBeingGCd (BookPageController oldPageController)
{
// --- IF YOU UNCOMMENT THIS, THE CRASHES GO AWAY, BUT THE PAGES ARE NOT GARBAGE COLLECTED AND AFTER MANY PAGES IPHONE IS OUT OF MEMORY AND IT CRASHES THE APP
if (parentController.book_page_controllers_reference_list.Contains (currentPageController) == false)
parentController.book_page_controllers_reference_list.Add (currentPageController);
}
I've already submitted the project tarball to the Xamarin team, but they weren't able to solve the problem.
I'm pretty sure the person assigned to your case will come up with the solution. The bigger the test case the more time it can take.
From a quick view the following, in your AppDelegate.cs, is wrong:
PageTurnViewController viewController = new PageTurnViewController ("PageTurnViewController", null);
window.AddSubview (viewController.View);
since the local viewController instance won't have any reference to it once FinishedLaunching returns and the GC will be able to collect it. However it's needed (on the native side) for keep the View fully valid. This can lead to crashes (there could be other cases too, that's the first and only file I checked this morning).
The solution is to promote the viewController to a field. That will make it alive even when the method returns, making it unavailable to collection.
UPDATE
I had a quick look at your code on github.
You are adding (sub)view but you never remove them (when the GC will Dispose them it won't remove them from the super view);
You are losing references to views, e.g. in PageDataSource.cs
newPageController = new BookPageController (nextPageIndex, parentController.currentPDFdocument, parentController);
return newPageController;
After the first page there will already be a reference stored in newPageController which will be overwritten and make the object collectable bug the GC. Since (sub)views are never removed there could still be native reference to them leading to crashes.
For debugging you can add your own finalizers, e.g.
~BookPageController ()
{
Console.WriteLine ("bu-bye");
}
and put breakpoints in them. If they get hit, while you think it's still in use, then you likely found a problem.
Since you are taking a dependency on iOS 5 new features, you should also adopt the new View Controller Containment APIs in iOS 5 that solve a few problems with view controllers.
I suggest you check the WWDC Video and slides for for Session 102 "Implement UIViewController Containment".