Remove a MKPointAnnotation Object from a Mutable Array - ios

Question

I have a map app that allows the User to save annotations as a favorite to a mutable array. All favorite annotations can then be displayed when the User chooses to.
Annotations added to the mutable array are of the MKPointAnnotation class. I can correctly add annotations to the mutable array, but I haven't come up with a working solution that correctly removes a specific annotation from the mutable array. How can a specific annotation be removed from the mutable array that contains multiple annotations that were saved as favorites? Several non-working solutions are found in my sample code.
//** Correctly adds a favorite annotation to the mutable array favoriteAnnotationsArray **
-(void)addToFavoriteAnnotationsArray{
MKPointAnnotation *annotation = [[MKPointAnnotation alloc] init];
NSArray *components = [favoritesString componentsSeparatedByString:#","];
annotation.coordinate = CLLocationCoordinate2DMake([components[1] doubleValue], [components[0] doubleValue]);
annotation.title = [components[2] stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceAndNewlineCharacterSet];
[self.favoriteAnnotationsArray addObject:annotation];
}
//** Need to remove a favorite annotation from the mutable array favoriteAnnotationsArray **
-(void)removeObjectFromFavoriteAnnotationsArray{
MKPointAnnotation *annotation = [[MKPointAnnotation alloc] init];
NSArray *components = [favoritesString componentsSeparatedByString:#","];
annotation.coordinate = CLLocationCoordinate2DMake([components[1] doubleValue], [components[0] doubleValue]);
annotation.title = [components[2] stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceAndNewlineCharacterSet];
//** Used in first non-working solution below **
//NSMutableArray *objectToRemoveArray = [[NSMutableArray alloc] init];
//[objectToRemoveArray addObject:annotation];
//** The following three lines didn't remove any annotations from array **
//[self.favoriteAnnotationsArray removeObjectsInArray:objectToRemoveArray];
//[self.favoriteAnnotationsArray removeObject:annotation];
//[self.favoriteAnnotationsArray removeObjectIdenticalTo:annotation];
//** This only removes the last object in array and not necessarily the correct annotation to remove **
[self.favoriteAnnotationsArray removeLastObject];
}

Answer 1

You will need to specify an unique annotation from the favoriteAnnotationsArray in order for it o be removed successfully.
Maybe you can try something as follows:
-(void)removeAnnotationFromFavoriteAnnotationsArrayWithTitle: (NSString *) titleString {
for(int i=0; i<self.favoriteAnnotationsArray.count; i++) {
MKPointAnnotation *annotation = (MKPointAnnotation *)[self.favoriteAnnotationsArray objectAtIndex:i];
NSString * annotationTitle = annotation.title;
if([annotationTitle isEqualToString:titleString]) {
[self.favoriteAnnotationsArray removeObject:annotation];
break;
}
}
}
If title is not unique enough for you to differentiate between annotations, then you might consider subclassing MKAnnotation and add an unique property and pass it to the above function instead of the title.

Answer 2

One approach is to iterate through your annotation array and find the one to remove. For example:
- (void)addToFavoriteAnnotationsArray:(NSString *)string {
MKPointAnnotation *annotation = [[MKPointAnnotation alloc] init];
NSArray *components = [string componentsSeparatedByString:#","];
annotation.coordinate = CLLocationCoordinate2DMake([components[1] doubleValue], [components[0] doubleValue]);
annotation.title = [components[2] stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceAndNewlineCharacterSet];
[self.favoriteAnnotationsArray addObject:annotation];
}
- (void)removeObjectFromFavoriteAnnotationsArray:(NSString *)string {
NSArray *components = [string componentsSeparatedByString:#","];
NSString *titleOfAnnotationToRemove = [components[2] stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceAndNewlineCharacterSet];
CLLocationCoordinate2D coordinateOfAnnotationToRemove = CLLocationCoordinate2DMake([components[1] doubleValue], [components[0] doubleValue]);
for (NSInteger i = 0; i < self.favoriteAnnotationsArray.count; i++) {
id<MKAnnotation>annotation = self.favoriteAnnotationsArray[i];
if ([annotation.title isEqualToString:titleOfAnnotationToRemove] && coordinateOfAnnotationToRemove.latitude == annotation.coordinate.latitude && coordinateOfAnnotationToRemove.longitude == annotation.coordinate.longitude) {
[self.favoriteAnnotationsArray removeObjectAtIndex:i];
break;
}
}
}
Or if you wanted to match on title, alone, then remove the coordinates from the if statement above. Also note that I've added the string as a parameter to these methods. It's always better to pass a parameter to a method rather than relying upon some property.
Frankly, though, when the user is selecting one to remove, you probably don't want them to have to manually enter the name and coordinates again. You probably want them to pick one from the list. So you might show them a table view of the annotations and when they say they want to remove the third one, you'd do just pass the index to a method like this:
- (void)removeObjectFromFavoriteAnnotationsArray:(NSInteger)index {
[self.favoriteAnnotationsArray removeObjectAtIndex:index];
}
By the way, all of the above routines remove the annotation from your array. If you've also added this annotation to the map view, remember to remove it from there, too.