I have an NSDictionary which contains (my custom) GTPerson objects. GTPerson has an NSMutableSet *parents attribute, on which I use @property and @synthesize. Out of my NSDictionary, I want to filter all the GTPerson objects which don't have any parents, i.e. where the count of parents is 0. I'm using the following code: NSPredicate ...
In Cocoa, addObserver:forKeyPath:options:context: retains "neither the receiver, nor anObserver". Therefore I assume observing self is allowed; that is, it's perfectly valid to do something like [self addObserver:self forKeyPath...] As long as you remember to unregister self as an observer as the first thing in dealloc. Is this assump...
I can access the value like this: NSNumber* rotationZ = [myLayer valueForKeyPath:@"transform.rotation.z"]; But for some reason, if I try to KV-observe that key path, I get a compiler error. First, this is how I try to do it: [myLayer addObserver:self forKeyPath:@"transform.rotation.z" options:0 context:nil]; The compiler tells me: ...
I am sold on KVO but if used in the obvious way it is synchronous. I would like to use it in a situation where I am firing off many KVO messages in rapid succession and it is causing my app to grind to a halt as the KVO messages are handled. Can someone suggest an approach - perhaps using NSOperation or NSThread - that will work here. M...
I'm interested in running some methods when my UIView is changed, either through a frame change or an affine transformation. My best idea is to do this by observing value changes for: myView.frame and myView.transform. However, the view portion of UIViews is not Key-Value complaint. Fortunatly the model portion of the view, the CAL...
I'm seeing some quirky behaviour with Cocoa's KVC/KVO and bindings. I have an NSArrayController object, with its 'content' bound to an NSMutableArray, and I have a controller registered as an observer of the arrangedObjects property on the NSArrayController. With this setup, I expect to receive a KVO notification every time the array is ...
I am creating my own bindable custom treeview. For that I would like to observe NSTreeController for updates to its items' to-many-relationships. NSTreeController is bound to CD managed object context. Every depth level has its own CD Entity with parent/children/isLeaf properties. I need to maintain same hierarcy in the view (and order o...
Hi, Whenever i make a change in the objects in the first tab of my application the updates are automatically upated in tab 2 becuase it uses a fetchedResultsController. Now i have a third tab that should also update itself, but how can i do that? I only have a nsmangedObjectContext in the third tab to get the appropriate data. How can ...
I've got a window which reflects the status of an NSOperation. How should I bind the NSProgressIndicator to the NSOperation's progress-property? ...
Hi, I've a problem with KVO and I just can't find out what it is. I have a screen that can be used to edit or create a record. That record is represented by a model object that holds a number of variables of type NSString. The controller for that string has an instance variable to hold the model currently being worked on. When I open ...
By default, when I observe the value of a UISlider, it only updates once, when the slider is clicked, not continuously, even thought that is the slider's setting. Is there a way to get the continuous value change of the slider? ...
I need a bit of help with KVO, I'm about half way there. What I'm trying to do is trigger a method when something in an Tree Controller changes. So I 'm using this code to register as a KVO. [theObject addObserver: self forKeyPath: @"myKeyPath" options: NSKeyValueObservingOptionNew context: NUL...
if you tell an objective c object to removeObservers: for a key path and that key path has not been registered, it cracks the sads. like - 'Cannot remove an observer for the key path "theKeyPath" from because it is not registered as an observer.' is there a way to determine if an object has a registered observer, so i can do this if...
Hi Fellow iPhone Developers, I am an experienced software engineer but new to the iPhone platform. I have successfully implemented sub-classed view controllers and can push and pop parent/child views on the view controller stack. However, I have struck trouble while trying to update a view controller when an object is edited in a child ...
I'd like to monitor an NSCountedSet to see if its contents changes. Setting up KVO seems to compile but it's not being triggered. First question: can you observe a set? If so then is there something wrong with this message? [subViewA addObserver:subViewB forKeyPath:@"countedSet" options:0 context:NULL]; I'm really just trying to m...
I was wondering what the parameters from this method would return. - (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context; In the documentation it says keyPath The key path, relative to ob...
The method - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { } has a parameter change which is a dictionary that contains information about the nature of the value change, how would I find out what was in this dictionary? ...
As explained in my earlier question … This code … - (void)syncKVO:(id)sender { NSManagedObjectContext *moc = [self managedObjectContext]; [syncButton setTitle:@"Syncing..."]; NSString *dateText = (@"Last Sync : %d", [NSDate date]); [syncDate setStringValue:dateText]; NSEntityDescription *entityDescription = [NSEntit...
I'm developing simple MVC app in Cocoa/Objective-C. I have a strange issue (or misunderstanding) with notifications and KVO. I have AppController object in MainMenu.xib, hence I implement awakeFromNib method where I register for NSImageView changing its image property. I add self as an observer in the following way: // options:3 equals...
When I bind a control to an NSArrayController using Interface Builder, there are a variety of options under the "Controller Key" field in the bindings inspector. I understand what "arrangedObjects" is, and I semi-understand what "selection" is, but I'd love to see a really nice explanation of all the options and when to use each one. Th...