Crashed while removing the pin from mapview - iphone

Question

I am working on MapView,on which I have two buttons.
1)centreButton:
this button drops the pin annotation at the centre of the current map.
when this button is pressed, I am storing the last annotation in a NSMutable array.
then remove the last annotation from mapview and drop one pin at the centre of map
Code I have done for this part is as follows:
function for dropping the pin
- (void)PinDropwithlatitude:(double)lat longitude:(double)longi droptitle:(NSString *)title
{
CLLocationCoordinate2D theCoordinate;
theCoordinate.latitude = lat;
theCoordinate.longitude = longi;
MKCoordinateRegion region;
region.center.latitude = theCoordinate.latitude;
region.center.longitude = theCoordinate.longitude;
//Set Zoom level using Span
MKCoordinateSpan span;
span.latitudeDelta =0.005;
span.longitudeDelta =0.005;
region.span = span;
[MapView setRegion:region animated:YES];
SetLat =lat;
SetLong =longi;
DDAnnotation *annotation = [[[DDAnnotation alloc] initWithCoordinate:theCoordinate addressDictionary:nil] autorelease];
annotation.title = title;
annotation.subtitle = [NSString stringWithFormat:#"%f %f", annotation.coordinate.latitude, annotation.coordinate.longitude];
[MapView addAnnotation:annotation];
}
when I press centre button I am doing the following code and store last array in annotation.
-(IBAction)CenterPressed:(id)sender
{
//40.439631,-3.698273 -spain centre
[lastAnnotation addObjectsFromArray:MapView.annotations];
NSLog(#"last annotation array=%#",lastAnnotation);
for (id annotation in [MapView annotations])
{
if ([annotation isKindOfClass:[MKUserLocation class]])
{
continue;
}
[MapView removeAnnotation:annotation];
}
[self PinDropwithlatitude:SetLat longitude:SetLong
droptitle:NSLocalizedString(#"Title", nil)];
}
the log for the array is showing me the
last annotations you can see below::
last annotation array=(
"<+40.43963100,-3.69827300> +/- 0.00m",
"<+40.43923187,-3.68722200> +/- 0.00m",
"<+40.43792343,-3.67670774> +/- 0.00m",
"<+40.43772888,-3.66711617> +/- 0.00m"
)
2)UNDOButton: which removes the currently placed annotation and redrop the previous annotation, for that i have removed the annotaion from mapview, and redrop the annotation last annotation from array which i have maintained previously,using the code:
-(IBAction)undoPressed:(id)sender
{
if ([lastAnnotation count]>0)
{
int countAnn = [lastAnnotation count];
[MapView removeAnnotation:[lastAnnotation objectAtIndex:countAnn-1]];
//[MapView delete:[lastAnnotation objectAtIndex:countAnn-1]];
[lastAnnotation removeObjectAtIndex:countAnn-1];
double latitude = [[[lastAnnotation objectAtIndex:[lastAnnotation count]-1] annotation]coordinate].latitude;
double longitude = [[[lastAnnotation objectAtIndex:[lastAnnotation count]-1]annotation]coordinate].longitude;
NSLog(#"count = %d",[lastAnnotation count]);
[self PinDropwithlatitude:latitude longitude:longitude droptitle:NSLocalizedString(#"Title", nil)];
}
}
but when i press the undo button it crashes with the following error
-[DDAnnotation annotation]: unrecognized selector sent to instance 0x79b8f40
I don't get to know, where exactly the problem arises. can any one please help me to point out my mistake in the above code.
thanks

Answer 1

can you try
[lastAnnotation lastObject]
instead of
[[lastAnnotation objectAtIndex:[lastAnnotation count]-1]
like
[MapView removeAnnotation:[lastAnnotation lastObject]];
[lastAnnotation removeObject:[lastAnnotation lastObject]];