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Questions tagged [key-value-observing]

Key-value Observing or KVO is a technology for observing changes in object properties.

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KVO - interface orientation property

I'm trying to observe interface orientation by KVO of UIViewController from other object by this code : [((UIViewController *)self.delegate) addObserver:self forKeyPath:@"interfaceOrientation" options:NSKeyValueObservingOptionNew context:NULL]; and…
Rivka Schwartz
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KVO mechanism throwing error?

I m implementing one photo edit app in which i have one camera captured image and one is output image which is i shown beside of captured image. Whenever i change my captured image scaling or rotation then i want notify this changes to outputImage.…
Tirth
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Two-way KVO: controller updates model, which notifies controller

I'm currently re-writing a form controller for iOS. It's a custom object that is bound to a model, and handles editing form fields, jumping to the prev/next field, handling custom keyboards, validating data... The first version was based on a plist…
Cyrille
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scroll table view while shrinking upper UIImage

I don't know if the title of this post is much descriptive so I'll try to explain it in more depth. I have this UserProfileViewController: The top part is an UIImage that has those buttons as subviews and also flips from side to side. The bottom…
alex
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Observing custom cell

I am trying to add observer (KVO) to observe my custom cell. Once the cell is selected I should receive a notification of the event. My code: [colMain addObserver:self forKeyPath:@"colMain" options:0…
uml
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Perform animations after one another, hit by KVO (after async URLRequest)

I want to insert UIViews dynamically with animation, based on incoming Data. I send two asynchronous URLRequests and get the received data back from another thread. I'm observing a property, which gets dynamically filled with data from different…
Fab1n
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Which observer pattern should I use for remote app?

I am building a remote app which is receiving different states of its accessory. It is receiving things like: power state on/off, volume state 5, equalizer setting jazz, etc. and has nothing more to do than map theses states into the UI with…
d.ennis
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Key-Value Observing an NSMutableArray within an NSMutableArray

Key-Value Observing the to-many relationship of an NSMutableArray seems like a good technique for automatically updating a tableview that has a single section and many rows. However, my table view is grouped and more naturally fits having an array,…
MaxGabriel
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NSTextField does not update calculated property using Core Data bindings

New to SO; my first question: Re: Core Data, document based app using bindings: I have an NSTableView bound to an NSArrayController, bound to an entity, LineItem, with several columns bound to the following LineItem attributes/properties: amount,…
averageJoe
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NSCollectionView implementation

I have looked at the documentation yet I still haven't successfully implemented a CollectionView. Here is what I have. My KVO/KVC compliant NSMutableArray. #import #import "ProjectModel.h" @interface KVOMutableArray :…
marcopolo
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Previously posted solution to getting Notification (on NSOperationQueue finishing all tasks) is not working for me

Get notification when NSOperationQueue finishes all tasks I have the same issue as the one posted by @porneL in the post above. I tried the solution posted by @NickForge (one that received 57 votes), but I am obviously doing it wrong because it does…
CoolDocMan
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KVO questions in a data source

I have a UITableView with a data source of NewsItem objects that is stored in an array. In my NewsItem object I have a BOOL called 'imageState' that I wanted to be tracked. I wanted to use KVO such that when the value of this imageState changed then…
adit
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Why is my observer unregistered?

I'm looking through my crash reports in TestFlight and the most frequent crash is: Cannot remove an observer "ListViewController 0x1d590500" for the key path "batchImageDownloadingInProgress" from "ListArchiver 0x1d5b83b0" because it is not…
djibouti33
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How should a virtual Core Data property be retained?

I have a NSManagedObject subclass with a virtual property which is expensive to calculate. The property depends on the value of one of the entity's concrete attributes. For performance reasons I only want to calculate the value of the virtual…
bluefloyd8
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KVO - problem retrieving object from storage and displaying for edition

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…
ruipacheco
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