I'm using Xcode 10.0 with swift 4.2 to learn about Key Value Coding from "Cocoa programming for OSX" I'm asked to create a simple class, which is a subclass of NSObject. The codes below: import C...

I have data = { 'first': { 'number': 1, 'text': 'Ya.' }, 'second': { 'number': 10, 'text': 'Da.' } }; And I really want to access it like: number = data['first.number']; Actually in ...

I was very happy to find Swift 3's implementation of #keyPath(), which will eliminate typos and enforce at compile time that the key path actually exists. Much better than manually typing Strings. ...

I have updated my code to swift 4 in Xcode 9. Before that it was working fine. But now AVplayer is crashing at observers below is the code where it is crashing. addObserver(self, forKeyPath: "pla...

I am learning how to use KVO. I created two classes, Truck and Driver as shown below. the Truck class has a textfield and a button, the text should contain the current truck speed, and when the bu...

I'm trying to understand some theory part in Objective C related to KVC. Following is the example I've done. I'm having class call Cookie and it has a property like below @property NSString *name...

My team has decided that new files should be written in swift, and I am seeing an odd problem with using KVC in an Objective-C object to set a property on a Swift object. My Objective-C sets a pro...

Is there a way to construct an NSPredicate so the following array can be filtered by average score larger than, say, 5? NSArray *objs = @[ @{@"scores":@[@3, @5, @2]}, @{@"scores":@[@5, @2, @8, @9]...

I'm using KVC to serialize an NSObject and attempt to save it to NSUserDefaults, which is giving me an Attempt to insert non-property value when I try to store my NSDictionary. Following are the p...

I have read the iOS-related chapters of Marcus S. Zarra's Core Data: Data Storage and Management for iOS, OS X, and iCloud (2nd edition) to great benefit. I am wondering about one aspect, though, w...

This is a mystery: I'm invoking setPrimitiveValue:forKey: on an NSManagedObject. The key is a legit, persistent, modeled attribute of the object. However, setPrimitiveValue:forKey: fails, often se...

In a nsobject you have a property "keyPath" you want to observe itself and you use [self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:nil]; Does the above lin...

I recently read some documentation and some blog entries about Key-Value Coding and found it extremely useful. I want to utilize it for my case, but I haven't been successful so far. In my case, I...

Which of the following is faster and why? CGFloat sum = 0; for (UIView *v in self.subviews) sum += v.frame.size.height; or CGFloat sum = [[self.subviews valueForKeyPath:@"@sum.frame.size.heig...

Let's assume we have an object of type person, which has a property called name. Person *p; [p setValue:@"John" forKey:@"name"]; This works very nicely. What I want to do is dig deeper. Say the ...

I can't figure out what @UnionOfObjects offers that a simple valueForKey: or valueForKeyPath: can't do. Apple docs: The @unionOfObjects operator returns an array containing the distinct object...

I've got an object of type id and would like to know if it contains a value for a given keyPath: [myObject valueForKeyPath:myKeyPath]; Now, I wrap it into a @try{ } @catch{} block to avoid excep...

I created an NSView subclass that has a float property and I'd like to set it in Interface Builder. In the User Defined Runtime Attributes section the only suitable Type is Number. But if I want to...

Before I switched to iOS development via Monotouch I played around a bit with ObjectiveC. Ever since one thing has been on my mind "Key Value Coding" (KVC). I have never understood what it is good ...