KVO crash NSKVODeallocate

This crash happens when an instance gets released before all key value observers pointing to its properties release. You need to call removeObserver:forKeyPath: before releasing the instance.

In another scenario, it will crash if you call removeObserver:forKeyPath: on an instance if none of the key value observers are pointing to its properties.

Convert iPad xib to iPhone version

We can go with the following approach to get iPhone version of iPad xibs already exist in the project. With this approach we no need to create a new xib and manually add all the subviews.

1. Xcode recognises the iPhone version of a XIB if the suffix is ~iphone (lowercase only) and iPad version if its ~ipad. If no suffix exists then it will consider it as an iPhone version. Lets suffix all the existing xib names with ~ipad.

2. Duplicate all the xib files and open them in TextEditor and do the following.

change “com.apple.InterfaceBuilder3.CocoaTouch.iPad.XIB” to “com.apple.InterfaceBuilder3.CocoaTouch.XIB”
change “iOS.CocoaTouch.iPad” to “iOS.CocoaTouch”
change iPad size (width=”1024″ height=“768”) to iPhone size (width=“320″ height=“568″)

3. Add the xib to the project and open it on Xcode.

4. Select the root view and go to the attributes inspector.

5. Change the orientation to portrait and size to Retina 4-inch Full Screen.

6. Adjust the frame of all the subviews.

Objective-C – How to use member variables in the categories.


@interface UIView (ObjectTagAdditions)
@property (nonatomic, retain) id objectTag;


#import <objc/runtime.h>
static char const * const ObjectTagKey = "ObjectTag";

@implementation UIView (ObjectTagAdditions)
@dynamic objectTag;

- (id)objectTag {
    return objc_getAssociatedObject(self, &ObjectTagKey);

- (void)setObjectTag:(id)newObjectTag {
    objc_setAssociatedObject(self, &ObjectTagKey, newObjectTag, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

Cited from : http://oleb.net/blog/2011/05/faking-ivars-in-objc-categories-with-associative-references/

Convert yyyy-MM-ddTHH:mm:ss.SSSZ format to default timezone

– (NSDate *) localDateStringForISODateTimeString:(NSString *) anISOString

NSDateFormatter *isoDateFormatter = [[NSDateFormatter alloc] init];
[isoDateFormatter setDateFormat:@”yyyy-MM-dd’T’HH:mm:ss.SSS’Z'”];
[isoDateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@”UTC”]];

NSDateFormatter *userFormatter = [[NSDateFormatter alloc] init];
[userFormatter setDateFormat:@”yyyy-MM-dd HH:mm:ss”];

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@”yyyy-MM-dd HH:mm:ss”];
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@”UTC”]];

NSDate *date = [isoDateFormatter dateFromString:anISOString];
return [dateFormatter dateFromString:[userFormatter stringFromDate:date]];

iOS orientation animation does not happen smoothly

If you apply any changes to the layer of underlying view.

for example,

shadowImageView.layer.masksToBounds = NO;
shadowImageView.layer.shadowOffset = CGSizeMake(-5, 0);
shadowImageView.layer.shadowOpacity = 1.0;