Key Value Coding is a mechanism for accessing an object’s properties indirectly, using strings to identify properties, rather than through invocation of an accessor method or accessing them directly through instance variables.
Questions tagged [key-value-coding]
390 questions
8
votes
3 answers
Key-Value-Observing a to-many relationship in Cocoa
I am trying to get key-value-observing to work for an NSMutableArray. Below is the .h file for MyObservee, the observed class:
@interface MyObservee : NSObject {
@private int someValue;
@private NSMutableArray *someArray;
}
@property…
Sam Lee
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8
votes
1 answer
How do I attatch a Key value pair to a UIView on iPhone?
When I started iPhone development, I read somewhere that it's possible to attach a key value pair to a UIView. I understood that all UIViews could be used as dictionaries to store any data you may want to attatch to them to prevent unnecessary…
Nick Cartwright
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7
votes
1 answer
Should "to-many" relationships be modelled as properties?
After reading the Key-Value Coding Programming Guide, the Key-Value Observing Programming Guide and the Model Object Implementation Guide, as well as reading many StackOverflow entries on the topic and experimenting with various modelling scenarios,…
Pascal Bourque
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7
votes
1 answer
KVO differentiating between willChangeValueForKey and didChangeValueForKey - are both necessary?
In line with Apple's own recommendations, when setting KVC/KVO compliant accessors manually, one should include BOTH KVO methods willChange and didChange. This is what I have done in all my manual accessor methods.
However,…
VectorVictor
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7
votes
4 answers
What does "Controller Key" mean in Interface Builder > Inspector > Bindings?
I can't find in the Docs where they explain all those fields and what they mean. Especially "Controller Key" is not clear to me.
Thanks
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7
votes
1 answer
iPhone key-value coding -- test for existence of key
Does iPhone key-value-coding have a way to test whether a class will accept a given key?
That is, without implementing the valueForUndefinedKey: or setValue: forUndefinedKey: method of the target class, I want to be able to do something like…
William Jockusch
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7
votes
1 answer
Why can I not use KVC from an Objective-C object to a Swift Property?
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 property like so: [textObject setValue:0.0…
A O
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7
votes
4 answers
Using Predicates on Array Objects in Swift returns Error
When I filter an array of custom Swift classes using a Predicate I get the error:
*** NSForwarding: warning: object 0x78ed21a0 of class 'Plantivo1_6.Seed' does not implement methodSignatureForSelector: -- trouble ahead
Unrecognized selector…
Timm Kent
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7
votes
4 answers
Key-Value Coding (KVC) with Array/Dictionary in Swift
Is it possible to key-value code (KVC) with native Swift data structures such as Array and Dictionary? Key-Value coding is still available for NSFoundation structures within Swift, just like in Objective C.
For example, this is valid:
var nsarray:…
kev
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7
votes
2 answers
How to create a predicate that compares all properties of an object?
For example, I have an object that has three properties: firstName, middleName, lastName.
If I want to search a string "john" in all the properties using NSPredicate.
Instead of creating a predicate like:
[NSPredicate…
David Liu
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7
votes
3 answers
NSManagedObject subclasses and setValuesForKeysWithDictionary:
I am initializing a NSManagedObject subclass using:
- (void)setValuesForKeysWithDictionary:(NSDictionary *)keyedValues
I am also knowingly giving it the undefined keys, which of course should throw an exception.
So, I have implemented:
-…
Corey Floyd
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7
votes
4 answers
#typedef and KVC in ObjC
I have a class that looks like this:
@interface Properties : NSObject {
@private
NSNumber* prop1;
NSNumberBool* prop2;
//etc
where NSNumberBool is a typedef:
// in MyApp_Prefix.pch
typedef NSNumber NSNumberBool;
I have all the required…
tba
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7
votes
1 answer
Key-Value Coding @UnionOfObjects
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
objects in the property specified by the key path to the…
Jesse Gumpo
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6
votes
1 answer
setNilValueForKey error
I have four textfields that bind to the model key path. If a number is typed into the textfield, everything works as planned. However, if the number is deleted then I get an error in the console with:
[Temperature 0x1003144b0 setNilValueForKey]:…
wigging
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6
votes
2 answers
Helper classes/libraries to make use of KVC/KVO on iOS more practical/safe?
This question is really looking for a specific class that I know exists, but cannot find.
A few weeks ago I read through an article outlining a helper class for using KVC - it let you encapsulate KVC subscriptions so that you could have multiple…
Kendall Helmstetter Gelner
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