Iphone – Experience with MKMapView Rotation

affinetransformcocoa-touchiphonemapkitmkmapview

I have an MKMapView that I am considering rotating in order to more conveniently display a series of Annotations to my users.

As of now I am planning on simply rotating the entire view with a CGAffineTransform, but I wanted to know if anyone had any experience with MKMapView rotation.

Are there any pitfalls or "gotchas" that you came across when adding rotation?
Is there an easier way to rotate a mapview?
If I have an overlay will the convertCoordinate:toPointToView: method still work the same way? I would assume that I'd have to apply the same transform to my overlay for the points to line up, but maybe the method is smarter than that.

If there's anything that you think could help out I'd love to hear it all.

Edit: After much experimentation I believe that I'll be using static maps that I can rotate and overlay myself, however, I would still be interested in any information about MKMapView rotation.

Best Answer

I also plan to use rotated MKMapView in my application. To show annotations unrotated I use the following code:

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation{
    ...
    annotationView.transform = GAffineTransformInvert(mapView.transform);
    ...
}

It seems to work for me.

Compare method

Either you implement a compare-method for your object:

- (NSComparisonResult)compare:(Person *)otherObject {
    return [self.birthDate compare:otherObject.birthDate];
}

NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(compare:)];

NSSortDescriptor (better)

or usually even better:

NSSortDescriptor *sortDescriptor;
sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthDate"
                                           ascending:YES];
NSArray *sortedArray = [drinkDetails sortedArrayUsingDescriptors:@[sortDescriptor]];

You can easily sort by multiple keys by adding more than one to the array. Using custom comparator-methods is possible as well. Have a look at the documentation.

Blocks (shiny!)

There's also the possibility of sorting with a block since Mac OS X 10.6 and iOS 4:

NSArray *sortedArray;
sortedArray = [drinkDetails sortedArrayUsingComparator:^NSComparisonResult(Person *a, Person *b) {
    return [a.birthDate compare:b.birthDate];
}];

Performance

The -compare: and block-based methods will be quite a bit faster, in general, than using NSSortDescriptor as the latter relies on KVC. The primary advantage of the NSSortDescriptor method is that it provides a way to define your sort order using data, rather than code, which makes it easy to e.g. set things up so users can sort an NSTableView by clicking on the header row.

Best Answer

Related Solutions

Ios – How to sort an NSMutableArray with custom objects in it

Compare method

NSSortDescriptor (better)

Blocks (shiny!)

Performance

Related Topic