Adding multiple overlays to MKMapView

Question

I am having some trouble understanding how to add multiple overlays to MKMapView. I have an array routes tracked. The routes tracked are arrays of CLLocations. So I have an array of arrays. I am able to take one route and draw it on the map view. However, I need to draw ALL the routes onto the map view. So here is how I go about creating the MKPolyline for 1 route: ``` -(void) loadRoute { //So we grab an array that holds all the locations of one route. NSArray *locations = [[NSArray alloc] initWithArray:[routesArray objectAtIndex:0]]; // while we create the route points, we will also be calculating the bounding box of our route // so we can easily zoom in on it. MKMapPoint northEastPoint; MKMapPoint southWestPoint; // create a c array of points. MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) *[locations count]); for(int idx = 0; idx < [locations count]; idx++) { CLLocation *tempLoc = (CLLocation*)[locations objectAtIndex:idx]; CLLocationDegrees latitude = tempLoc.coordin…

Accepted Answer

The `routeLine` and `routeLineView` variables can only point to one overlay and overlay view at a time so you would theoretically need an array of such variables.

However, based on the code shown, you don't need to keep references to these in the first place.

I suggest removing the `routeLine` and `routeLineView` variables.

Then you just create an overlay object locally and in `viewForOverlay` return a view for the requested `overlay` parameter.

In the `loadRoute` method, you can loop through the `routesArray` and for each route, create a local overlay object, and call `addOverlay` on it.

There's also an easier way to construct a map rect that bounds all the routes so you can set the map's region to show them all.

Example:

```
-(void) loadRoute
{
    _routeRect = MKMapRectNull;

for (int raIndex = 0; raIndex < routesArray.count; raIndex++) 
    {
        //So we grab an array that holds all the locations of one route. 
        NSArray *locations = [[NSArray alloc] initWithArray:
                                 [routesArray objectAtIndex:raIndex]];
        //note we are getting object at raIndex (not 0) above

//...no change to existing code here...

//self.routeLine = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
        //replace above line with this...
        MKPolyline *pl = [MKPolyline polylineWithPoints:pointArr count:[locations count]];
        [mapView addOverlay:pl];

//Zoom in to fit route on screen
        //_routeRect = MKMapRectMake(southWestPoint.x, southWestPoint.y, northEastPoint.x - southWestPoint.x, northEastPoint.y - southWestPoint.y);
        //replace above line with this to create a rect around ALL routes...
        if (MKMapRectIsNull(_routeRect))
            _routeRect = pl.boundingMapRect;
        else
            _routeRect = MKMapRectUnion(_routeRect, pl.boundingMapRect);

// clear the memory allocated earlier for the points
        free(pointArr);
    }    
}
```

In `viewDidLoad`, just call `loadRoute` and don't call `addOverlay`.

The `viewForOverlay` method becomes much simpler:

```
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
    MKPolylineView *pv = [[MKPolylineView alloc] initWithPolyline:overlay];
    pv.fillColor = [UIColor redColor];
    pv.strokeColor = [UIColor redColor];
    pv.lineWidth = 3;
    return pv;
}
```

By the way, in `loadRoute`, this line:

```
MKMapPoint* pointArr = malloc(sizeof(CLLocationCoordinate2D) *[locations count]);
```

should be:

```
MKMapPoint* pointArr = malloc(sizeof(MKMapPoint) *[locations count]);
```

It should use the size of `MKMapPoint` (not `CLLocationCoordinate2D`). They are not the same thing (even though the structs happen to be the same byte size).

Adding multiple overlays to MKMapView

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