Why NSUserDefaults failed to save NSMutableDictionary in iOS?

by

I found out one alternative, before save, I encode the root object (NSArray object) using NSKeyedArchiver, which ends with NSData. Then use UserDefaults save the NSData.

When I need the data, I read out the NSData, and use NSKeyedUnarchiver to convert NSData back to the object.

It is a little cumbersome, because i need to convert to/from NSData everytime, but it just works.

Here is one example per request:

Save:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray *arr = ... ; // set value
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:arr];
[defaults setObject:data forKey:@"theKey"];
[defaults synchronize];

Load:

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [defaults objectForKey:@"theKey"];
NSArray *arr = [NSKeyedUnarchiver unarchiveObjectWithData:data];

The element in the array implements 

@interface CommentItem : NSObject<NSCoding> {
    NSString *value;
}

Then in the implementation of CommentItem, provides two methods:

-(void)encodeWithCoder:(NSCoder *)encoder
{
    [encoder encodeObject:value forKey:@"Value"];
}

-(id)initWithCoder:(NSCoder *)decoder
{
    self.value = [decoder decodeObjectForKey:@"Value"];
    return self;
}

Anyone has better solution?

Thanks everyone.

More Related Contents:

  1. Save string to the NSUserDefaults?
  2. Clearing NSUserDefaults
  3. Delete all keys from a NSUserDefaults dictionary iOS
  4. Setting a button’s target/action and passing a particular string to the action [closed]
  5. How to programmatically send SMS on the iPhone?
  6. Placeholder in UITextView
  7. Get to UIViewController from UIView?
  8. How to intercept touches events on a MKMapView or UIWebView objects?
  9. Remove HTML Tags from an NSString on the iPhone
  10. Having a UITextField in a UITableViewCell
  11. How do I wrap text in a UITableViewCell without a custom cell
  12. How do I make UILabel display outlined text?
  13. Fade/dissolve when changing UIImageView’s image
  14. How to disable/enable the return key in a UITextField?
  15. How do I scroll the UIScrollView when the keyboard appears?
  16. in iPhone App How to detect the screen resolution of the device
  17. Counting the number of lines in a UITextView, lines wrapped by frame size
  18. Center content of UIScrollView when smaller
  19. Can I get a NSURL from an XCAssets bundle?
  20. Send a file as attachment in objective c
  21. How to change UINavigationBar background color from the AppDelegate
  22. How can I delay a method call for 1 second?
  23. Getting the Value of a UITextField as keystrokes are entered?
  24. Storing authentication tokens on iOS – NSUserDefaults vs Keychain?
  25. Setting scroll position in UITableView
  26. Creating iPhone Pop-up Menu Similar to Mail App Menu
  27. UITextView cursor below frame when changing frame
  28. Dismissing both UINavigation views and Modal views at once programmatically
  29. UIView’s border color in Interface builder doesn’t work?
  30. Email validation on textField in iOS

Leave a Comment