Where’s the difference between setObject:forKey: and setValue:forKey: in NSMutableDictionary?

by

setValue:forKey: is part of the NSKeyValueCoding protocol, which among other things, lets you access object properties from the likes of Interface Builder. setValue:forKey: is implemented in classes other than NSDictionary.

setObject:forKey: is NSMutableDictionary's reason to exist. Its signature happens to be quite similar to setValue:forKey:, but is more generic (e.g. any key type). It’s somewhat of a coincidence that the signatures are so similar.

What adds to the confusion is that NSMutableDictionary’s implementation of setValue:forKey: is equivalent to setObject:forKey: in most cases. In other classes, setValue:forKey: changes member variables. In NSMutableDictionary, it changes dictionary entries, unless you prefix the key with a ‘@’ character — in which case it modifies member variables.

So, in a nutshell, use setObject:forKey: when you need to work with dictionary keys and values, and setValue:forKey: in the rarer cases where you need to tackle KVP.

EDIT: and oh, it looks like this has been asked and answered before: Difference between objectForKey and valueForKey?

More Related Contents:

  1. how to remove " in json string?
  2. How to make UI with round image and round text, also add ratting icon on same circle. in iOS application
  3. How do I set up a simple delegate to communicate between two view controllers?
  4. Launch an app from within another (iPhone)
  5. How can I send mail from an iPhone application
  6. iPhone App Minus App Store?
  7. How to animate the background color of a UILabel?
  8. Cocoa Graphing/Plotting Framework on iOS [closed]
  9. “From View Controller” disappears using UIViewControllerContextTransitioning
  10. Given a view, how do I get its viewController?
  11. UIPopoverPresentationController on iPhone doesn’t produce popover
  12. Steps to upload an iPhone application to the AppStore
  13. Change the color of default red color delete button in UITableViewCell when swiping rows or click on edit button
  14. Application crashed while importing songs from Ipod library in iPhone for iOs 5.0
  15. UIView shake animation
  16. Control cursor position in UITextField
  17. Entitlements file do not match those specified in your provisioning profile.(0xE8008016)
  18. Moving the cursor to the beginning of UITextField
  19. How to hide status bar in UIImagepickercontroller?
  20. How to maintain presenting view controller’s orientation when dismissing modal view controller?
  21. Converting iPhone xib to iPad xib?
  22. How to get UIKeyboard size with iOS
  23. how to programmatically fake a touch event to a UIButton?
  24. SwiftUI: Set Status Bar Color For a Specific View
  25. Take screenshots in the iOS simulator
  26. Will iOS region monitoring call didEnterRegion on my app if my app is in a terminated state?
  27. Change the color of a link in an NSMutableAttributedString
  28. How to get back “Allow Push Notifications” dialog after it was dismissed once?
  29. Enable/Disable Apple Push Notification from iPhone app?
  30. Disable bounce effect in UIPageViewController [duplicate]

Leave a Comment