iPhone: How to detect if an EKEvent instance can be modified?

Question

While working with the EventKit on iPhone I noticed that some events can exist which cannot be modified. Examples I encountered so far are birthdays and events synced with CalDAV. When you view the event's details in the standard built-in calendar app on iPhone the "Edit" button in the top-right corner is not visible in these cases, where it would be visible when viewing "normal" events.

I've searched everywhere, read all documentation there is but I simply can't find anything that tells me how to detect this behavior! I can only detect it afterwards:

1. edit an event's title
2. save it to the event store
3. check the event's title, if it has not changed it is not editable!

I am looking for a way that I can detect the non-editable behavior of an event beforehand. I know this is possible because I've seen other calendar apps implement this correctly.

Answer 1

Ok it appears as if the SDK doesn't provide me with anything I can use to check if an EKEvent is read-only. I created a workaround by creating a category that adds an "isReadOnly" method to all EKEvent instances.

EKEvent+ReadOnlyCheck.h

@interface EKEvent(ReadOnlyCheck)
- (BOOL) isReadOnly;
@end`

EKEvent+ReadOnlyCheck.m

#import "EKEvent+ReadOnlyCheck.h"

@implementation EKEvent(ReadOnlyCheck)

- (BOOL) isReadOnly {
    BOOL readOnly;
    NSString *originalTitle = [self.title retain];
    NSString *someRandomTitle = [NSString stringWithFormat:@"%i", arc4random()];

    self.title = someRandomTitle;
    readOnly = [originalTitle isEqualToString:self.title];
    self.title = originalTitle;
    [originalTitle release];

    return readOnly;
}
@end

When the above files are in place I can simply call isReadOnly on the EKEvent of my choice.

#import "EKEvent+ReadOnlyCheck.h"
...
if ([event isReadOnly]) {
    // Do your thing
}
...