How to store CGRect values in NSMutableArray?

You need to wrap the CG structures in NSValue classes. So:

NSMutableArray* array = [NSMutableArray mutableArray];
[array addObject:[NSValue valueWithCGRect:CGRectMake(0,0,10,10)]];
CGRect someRect = [[array objectAtIndex:0] CGRectValue];

CGRect rect = CGRectMake( 5, 5, 40, 30 );
NSString* rectAsString = NSStringFromCGRect( rect );
CGRect original = CGRectFromString( rectAsString );

We store the CGRect,CGPoint,CMTime objects in a NSMutableArray,

[arrayName addObject:[NSValue valueWithCGPoint:MyCGPoint]]

[arrayName addObject:[NSValue valueWithCGRect:MyCGRect]]

[arrayName addObject:[NSValue valueWithCMTime:MyCMTime]]

[arrayName addObject:[NSValue valueWithCMTimeRange:MyCMTimeRange]]

Store string in array.and then get back string and convert that in CGRect back as per the need.
CGRect rect = CGRectMake( 5, 5, 40, 30 );
NSString* rectAsString = NSStringFromCGRect( rect );
NSMutableArray* array = [NSMutableArray mutableArray];
[array addObject:rectAsString];

For converting string in CGRect back use:-
CGRect rect9 = CGRectFromString(rectAsString);