I am having a really weird issue when testing on my 1st gen. iPad (running iOS 5).
I have a UIView that I use as a property (with retain). I nil the property in the parent view's dealloc method. Pretty basic stuff. It works perfect on my iPad 3 running iOS 6, but doesn't get released on my 1st gen.
Any ideas what might be going on?
I'm not using ARC.
If you're retaining it, you have to release it. You can't just nil the instance variable.
So if you're property looks like this:
#property (nonatomic, retain) UIView *myView;
You're dealloc would either look like this:
- (void)dealloc
{
[myView release], myView = nil;
[super dealloc];
}
Or this:
- (void)dealloc
{
[self setMyView:nil];
[super dealloc];
}
Or this:
- (void)dealloc
{
self.myView = nil;
[super dealloc];
}
And your property will properly get released--unless something else is retaining it.
So I figured this out. It seems to be a bug in the iOS 6 SDK or maybe I just don't understand it. I have a UIViewController that presents another vc via presentViewController:animated:completion: —If I dismiss the presented vc then it releases and subsequently all subviews are removed and all is well.
However, if while the presented vc is showing, I remove/destroy the parent vc, the presented vc is deallocated but, its subviews are not told to removeFromSuperview; This doesn't show up as a leak in instruments, BUT it does prevent the subviews from deallocating.
This does not happen on iOS 6, thus I suspect this is a bug in iOS 5. Everything releases/deallocates as one would expect on iOS 6.
If someone has an explanation, or a better understanding of this, I would love to reward the answer to them instead of myself.
A view controller isn't responsible for removing its view from the superview when the view controller is dealloc'ed. The view controller is just responsible for releasing its own reference to it.
For example: you can create a view controller, ask for its view, then add that view to another view and throw away the view controller. In that case, you're just using the view controller as a view builder.
I'm not sure why the behavior is different in iOS 6, but would love to know.
Related
I've got plenty of experience with iOS, but Cocoa has me a bit confused. I read through several Apple docs on Cocoa but there are still details that I could not find anywhere. It seems the documentation was written before the NSDocument-based Xcode template was updated to use NSViewController, so I am not clear on how exactly I should organize my application. The template creates a storyboard with an NSWindow, NSViewController.
My understanding is that I should probably subclass NSWindowController or NSWindow to have a reference to my model object, and set that in makeWindowControllers(). But if I'd like to make use of the NSViewController instead of just putting everything in the window, I would also need to access my model there somehow too. I notice there is something called a representedObject in my view controller which seems like it's meant to hold some model object (to then be cast), but it's always nil. How does this get set?
I'm finding it hard to properly formulate this question, but I guess what I'm asking is:how do I properly use NSViewController in my document-based application?
PS: I understand that NSWindowController is generally meant to managing multiple windows that act on one document, so presumably if I only need one window then I don't need an NSWindowController. However, requirements might change and having using NSWindowController may be better in the long run, right?
I haven't dived into storyboards but here is how it works:
If your app has to support 10.9 and lower create custom of subclass NSWindowController
Put code like this into NSDocument subclass
- (void)makeWindowControllers
{
CustomWindowController *controller = [[CustomWindowController alloc] init];
[self addWindowController:controller];
}
If your app has multiple windows than add them here or somewhere else (loaded on demand) but do not forget to add it to array of document windowscontroller (addWindowController:)
If you create them but you don't want to show all the windows then override
- (void)showWindows
{
[controller showWindow:nil]
}
You can anytime access you model in your window controller
- (CustomDocument *)document
{
return [self document];
}
Use bindings in your window controller (windowcontroller subclass + document in the keypath which is a property of window controller)
[self.textView bind:#"editable"
toObject:self withKeyPath:#"document.readOnly"
options:#{NSValueTransformerNameBindingOption : NSNegateBooleanTransformerName}];
In contrast to iOS most of the views are on screen so you have to rely on patterns: Delegation, Notification, Events (responder chain) and of course MVC.
10.10 Yosemite Changes:
NSViewController starting from 10.10 is automatically added to responder chain (generally target of the action is unknown | NSApp sendAction:to:from:)
and all the delegates such as viewDidLoad... familiar from iOS are finally implemented. This means that I don't see big benefit of subclassing NSWindowCotroller anymore.
NSDocument subclass is mandatory and NSViewController is sufficient.
You can anytime access you data in your view controller
- (CustomDocument *)document
{
return (CustomDocument *)[[NSDocumentController sharedDocumentController] documentForWindow:[[self view] window]];
//doesn't work if you do template approach
//NSWindowController *controller = [[[self view] window] windowController];
//CustomDocument *document = [controller document];
}
If you do like this (conforming to KVC/KVO) you can do binding as written above.
Tips:
Correctly implement UNDO for your model objects in Document e.g. or shamefully call updateChangeCount:
[[self.undoManager prepareWithInvocationTarget:self] deleteRowsAtIndexes:insertedIndexes];
Do not put code related to views/windows into your Document
Split your app into multiple NSViewControllers e.g.
- (void)prepareForSegue:(NSStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:AAPLListWindowControllerShowAddItemViewControllerSegueIdentifier]) {
AAPLListViewController *listViewController = (AAPLListViewController *)self.window.contentViewController;
AAPLAddItemViewController *addItemViewController = segue.destinationController;
addItemViewController.delegate = listViewController;
}
}
Previous code is called on windowcontroller with viewcontroller as delegate (again possible only after 10.10)
I always prefer to use multiple XIBs rather than one giant storyboard/XIB. Use following subclass of NSViewController and always inherit from it:
#import <Cocoa/Cocoa.h>
#interface MyViewController : NSViewController
#property(strong) IBOutlet NSView *viewToSubstitute;
#end
#import "MyViewController.h"
#interface MyViewController ()
#end
#implementation MyViewController
- (void)awakeFromNib
{
NSView *view = [self viewToSubstitute];
if (view) {
[self setViewToSubstitute:nil];
[[self view] setFrame:[view frame]];
[[self view] setAutoresizingMask:[view autoresizingMask]];
[[view superview] replaceSubview:view with:[self view]];
}
}
#end
Add a subclass of MyViewController to the project with XIB. Rename the XIB
Add NSViewController Object to the XIB and change its subclass name
Change the loading XIB name to name from step 1
Link view to substitute to the view you want to replace
Check example project Example Multi XIB project
Inspire yourself by shapeart or lister or TextEdit
And a real guide is to use Hopper and see how other apps are done.
PS: You can add your views/viewcontroller into responder chain manually.
PS2: If you are beginner don't over-architect. Be happy with the fact that your app works.
I'm relatively new to this myself but hopefully I can add a little insight.
You can use the view controllers much as you would in ios. You can set outlets and targets and such. For NSDocument-based apps you can use a view controller or the window controller but I think for most applications you'll end up using both with most of the logic being in the view controller. Put the logic wherever it makes the most sense. For example, if your nsdocument can have multiple window types then use the view controller for logic specific to each type and the window controller for logic that applies to all the types.
The representedObject property is primarily associated with Cocoa bindings. While I am beginning to become familiar with bindings I don't have enough background to go into detail here. But a search through the bindings programming guide might be helpful. In general bindings can take the place of a lot of data source code you would need to write on ios. When it works it's magical. When it doesn't work it's like debugging magic. It can be a challenge to see where things went wrong.
Let me add a simple copy-pastable sample for the short answer category;
In your NSDocument subclass, send self to the represented object of your view controller when you are called to makeWindowControllers:
- (void) makeWindowControllers
{
NSStoryboard* storyboard = [NSStoryboard storyboardWithName: #"My Story Board" bundle: nil];
NSWindowController* windowController = [storyboard instantiateControllerWithIdentifier: #"My Document Window Controller"];
MyViewController* myController = (id) windowController.contentViewController;
[self addWindowController: windowController];
myController.representedObject = self;
}
In you MyViewController subclass of NSViewController, overwrite setRepresentedObject to trap it's value, send it to super and then make a call to refresh your view:
- (void) setRepresentedObject: (id) representedObject
{
super.representedObject = representedObject;
[self myUpdateWindowUIFromContent];
}
Merci, bonsoir, you're done.
The upcoming OSX 10.10 ("Yosemite") offers a new type of view, NSVisualEffectView, which supports through-the-window or within-the-window translucency. I'm mostly interested in through-the-window translucency, so I'm going to focus on that in this question, but it applies to within-the-window translucency as well.
Using through-the-window translucency in 10.10 is trivial. You just place an NSVisualEffectView somewhere in your view hierarchy and set it's blendingMode to NSVisualEffectBlendingModeBehindWindow. That's all it takes.
Under 10.10 you can define NSVisualEffectViews in IB, set their blending mode property, and you're off and running.
However, if you want to be backwards-compatible with earlier OSX versions, you can't do that. If you try to include an NSVisualEffectView in your XIB, you'll crash as soon as you try to load the XIB.
I want a "set it and forget it" solution that will offer translucency when run under 10.10 and simply degrade to an opaque view when run on earlier OS versions.
What I've done so far is to make the view in question a normal NSView in the XIB, and then add code (called by awakeFromNib) that checks for [NSVisualEffectView class] != nil, and when it's the class is defined, I create an instance of the NSVisualEffectView, move all my current view's subviews to the new view, and install it in place. This works, but it's custom code that I have to write every time I want a translucent view.
I'm thinking this might be possible using an NSProxy object. Here's what I'm thinking:
Define a custom subclass of NSView (let's call it MyTranslucentView). In all the init methods (initWithFrame and initWithCoder) I would throw away the newly created object and instead create a subclass of NSProxy that has a private instance variable (myActualView). At init time it would decide to create the myActualView object as an NSVisualEffectView if OS>=10.10, and a normal NSView under OS<10.10.
The proxy would forward ALL messages to it's myActualView.
This would be a fair amount of fussy, low-level code, but I think it should work.
Has anybody done something like this? If so, can you point me in the right direction or give me any pointers?
Apple is MUCH more open with the Beta agreement with Yosemite a than with previous Betas. I don't think I'm violating my Beta NDA by talking about this in general terms, but actual code using NSVisualEffectView would probably need to be shared under NDA...
There is a really simple, but somewhat hacky solution: Just dynamically create a class named NSVisualEffectView when your app starts. Then you can load nibs containing the class, with graceful fallback on OS X 10.9 and earlier.
Here's an extract of my app delegate to illustrate the idea:
AppDelegate.m
#import "AppDelegate.h"
#import <objc/runtime.h>
#implementation PGEApplicationDelegate
-(void)applicationWillFinishLaunching:(NSNotification *)notification {
if (![NSVisualEffectView class]) {
Class NSVisualEffectViewClass = objc_allocateClassPair([NSView class], "NSVisualEffectView", 0);
objc_registerClassPair(NSVisualEffectViewClass);
}
}
#end
You have to compile this against the OS X 10.10 SDK.
How does it work?
When your app runs on 10.9 and earlier, [NSVisualEffectView class] will be NULL. In that case, the following two lines create a subclass of NSView with no methods and no ivars, with the name NSVisualEffectView.
So when AppKit now unarchives a NSVisualEffectView from a nib file, it will use your newly created class. That subclass will behave identically to an NSView.
But why doesn't everything go up in flames?
When the view is unarchived from the nib file, it uses NSKeyedArchiver. The nice thing about it is that it simply ignores additional keys that correspond to properties / ivars of NSVisualEffectView.
Anything else I need to be careful about?
Before you access any properties of NSVisualEffectView in code (eg material), make sure that the class responds to the selector ([view respondsToSelector:#selector(setMaterial:)])
[[NSVisualEffectView alloc] initWithFrame:] still wont work because the class name is resolved at compile time. Either use [[NSClassFromString(#"NSVisualEffectView") alloc] initWithFrame:], or just allocate an NSView if [NSVisualEffectView class] is NULL.
I just use this category on my top-level view.
If NSVisualEffects view is available, then it inserts a vibrancy view at the back and everything just works.
The only thing to watch out for is that you have an extra subview, so if you're changing views around later, you'll have to take that into account.
#implementation NSView (HS)
-(instancetype)insertVibrancyViewBlendingMode:(NSVisualEffectBlendingMode)mode
{
Class vibrantClass=NSClassFromString(#"NSVisualEffectView");
if (vibrantClass)
{
NSVisualEffectView *vibrant=[[vibrantClass alloc] initWithFrame:self.bounds];
[vibrant setAutoresizingMask:NSViewWidthSizable|NSViewHeightSizable];
[vibrant setBlendingMode:mode];
[self addSubview:vibrant positioned:NSWindowBelow relativeTo:nil];
return vibrant;
}
return nil;
}
#end
I wound up with a variation of #Confused Vorlon's, but moving the child views to the visual effect view, like so:
#implementation NSView (Vibrancy)
- (instancetype) insertVibrancyView
{
Class vibrantClass = NSClassFromString( #"NSVisualEffectView" );
if( vibrantClass ) {
NSVisualEffectView* vibrant = [[vibrantClass alloc] initWithFrame:self.bounds];
[vibrant setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
NSArray* mySubviews = [self.subviews copy];
for( NSView* aView in mySubviews ) {
[aView removeFromSuperview];
[vibrant addSubview:aView];
}
[self addSubview:vibrant];
return vibrant;
}
return nil;
}
#end
update 2
viewDidAppear is executed twice, once before and once after, the overlay button is touched. Would a fix be to add a conditional to viewDidAppear which would return control to the calling class? If so, I would appreciated suggestions. Or maybe the very fact that viewDidAppear execute twice suggests another approach to a fix?
update 2
update 1
Maybe the problem is my usage of viewDidAppear and viewDidLoad shown below. Can anyone help, please?
- (void)viewDidAppear:(BOOL)animated
{
self.overlayViewController = [[BSsetupOverlayViewController alloc] initWithNibName:#"BSsetupOverlayViewController" bundle:nil] ;
// as a delegate we will be notified when pictures are taken and when to dismiss the image picker
self.overlayViewController.delegate = self;
[self showImagePicker:UIImagePickerControllerSourceTypeCamera];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
}
update 1
update 0
Perhaps I was not clear that the difference between the version that does not work and the one that does is that Storyboard is used in the one that does not work. Why would a done button work without Storyboard, but not with, even though only a nib is involved with the overlay?
update 0
The UIButton here was able to dismiss the camera preview, but in my actual app, tapping the UIButton only temporarily dismisses the preview and overlay screen. Immediately the preview returns. I think the problem is with the way I am implementing the delegate to the UIImagePicker, but I may be wrong.
I have created setup.zip here which contains a sample project with the undesirable behavior.
I took this question to the North Atlanta iOS Meetup and suggested that a conditional clause might fix the problem, as I mentioned in update 2 of the question. The founder of the Meetup, Kurt Niemi, quickly showed how to do so by editing the BSsetupViewController class.
First he added a Boolean property to the interface.
#property (nonatomic, assign) BOOL alreadyDisplayed;
Second he added a clause to the viewDidAppear method.
if (self.alreadyDisplayed)
{
self.alreadyDisplayed = FALSE;
[self dismissViewControllerAnimated:NO completion:nil];
return;
}
self.alreadyDisplayed = TRUE;
And last he added a slight unnecessary clause to the viewDidLoad method.
self.alreadyDisplayed = FALSE;
I still wish these steps were unnecessary, but they seem to work.
I have just started developing iPad apps and I'm struggling with an issue for too long now, so I've decided to go for help.
I have an application for iPad using storyboard and started as a Tabbed application using CoreData. So the issue is, my NSManagedObjectContext starts with a value but when I move to another tab, the managedObjectContext becomes null.
Don't know what to do. Some help would be greatly appreciated.
Thanks
Elkucho
I'm slightly confused...
self.window.rootViewController
should return your instance of UITabBarController, which should not respond to setManagedObjectContext: and therefore should crash.
With this in mind what you need to do it
Get the tabBarController
Cycle through the viewController's that the tabBarController manages
Pass them the managedObjectContext
for (id viewController in self.window.rootViewController.viewControllers) {
[viewController setManagedObjectContext:self.managedObjectContext];
}
Edit
I've taken a quick look.
You rarely need to subclass UITabBarController and you don't really need to in this case.
What you want to do is just get the managedObjectContext to each of the viewControllers in the tabBarController, the tabBarController itself does need to know about it.
I changed your application:didFinishLaunchingWithOptions: to the following and it worked the way it was supposed to
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
UITabBarController *tabBarController = (id)self.window.rootViewController;
for (id viewController in tabBarController.viewControllers) {
[viewController setManagedObjectContext:self.managedObjectContext];
}
}
I am new to iOS Development and am wondering how to put a scrollview in a storyboard, using Xcode 4.2. I want the content to be 1280 by 460. This code all works well, but when I go to wire up the outlet, there is no file's owner, so i'm stumped. Here is the code I have:
in the .h file-
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController {
IBOutlet UIScrollView *scrollView;
}
#end
and the .m, under viewDidLoad:
- (void)viewDidLoad
{
[scrollView setScrollEnabled:YES];
[scrollView setContentSize:CGSizeMake(1280,460)];
[scrollView setPagingEnabled:YES];
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
If anyone could help me, that would be great!
Storyboards do not have a File's Owner. You need to use the View Controller to connect the Outlets instead. I.E. Drag to the View Controller in the same way you used to drag to the File's Owner.
OK, I figured it out. I just had to create a class for my view controller. I was trying to use files that were not part of a class that was a subclass of UIViewController.I had to create a new class, then copy the old code in and make my view controller's class that of the NEW files, and THEN wire up the outlets. I was changing the class to something that was not there. I then wired my outlet up to the scroll view I wanted. Thankfully, that part is finally over! Thanks for the suggestions, guys, I really appreciate it.
A good visual tutorial is in the current Stanford CS193p course for iOS 5 in iTunes U.
This course works mainly with storyboards and they cover among other things UIScrollViews