How to select map pin when tapping table row that associates with it?

Question

Here I have 2 views:

• WallViewController
• TableViewController

WallViewController contains MKMapView, and TableViewController is a subclass of PFQueryTableViewController displaying rows of content that associate with annotation pin on WallViewController. TableViewController is added as subview in WallViewController, so these 2 views are displayed together. Now when I tap annotation pin on the map, the tableview in TableViewController will scroll to the row that associates with that annotation pin selected successfully. But what I want to do is to also have a reversed action of that, so when I tap a row, the annotation pin that associates with that row will be selected and also its callout will be displayed.

Here below I provided relevant codes:

WallViewController.h

@interface WallViewController : UIViewController <MKMapViewDelegate, CLLocationManagerDelegate>

@property (nonatomic, strong) IBOutlet MKMapView *mapView;
@end

@protocol WallViewControllerHighlight <NSObject>
- (void)highlightCellForPost:(PAWPost *)post;
- (void)unhighlightCellForPost:(PAWPost *)post;
@end

WallViewController.m

- (void)viewDidLoad {
    [super viewDidLoad];
    self.tableViewController = [[TableViewController alloc] initWithStyle:UITableViewStylePlain];
    [self addChildViewController:self.tableViewController];

    self.tableViewController.view.frame = CGRectMake(6.0f, 215.0f, 308.0f, self.view.bounds.size.height - 215.0f);
    [self.view addSubview:self.tableViewController.view];
    self.wallPostsTableViewController.wallViewController = self;
    ....
    }

- (void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view {
    id<MKAnnotation> annotation = [view annotation];
    if ([annotation isKindOfClass:[PAWPost class]]) {
        PAWPost *post = [view annotation];                        
        [PostsTableViewController highlightCellForPost:post];
    } else if ([annotation isKindOfClass:[MKUserLocation class]]) {
        // Center the map on the user's current location:
        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        MKCoordinateRegion newRegion = MKCoordinateRegionMakeWithDistance(appDelegate.currentLocation.coordinate, appDelegate.filterDistance * 2, appDelegate.filterDistance * 2);

        [self.mapView setRegion:newRegion animated:YES];
        self.mapPannedSinceLocationUpdate = NO;
    }
}

TableViewController.h

@interface TableViewController : PFQueryTableViewController <WallViewControllerHighlight>

@property (nonatomic, strong)  PAWWallViewController *wallViewController;
- (void)highlightCellForPost:(PAWPost *)post;
- (void)unhighlightCellForPost:(PAWPost *)post;
@end

TableViewController.m

....
@synthesize wallViewController;
....

- (void)highlightCellForPost:(PAWPost *)post {
    // Find the cell matching this object.
    for (PFObject *object in [self objects]) {
        PAWPost *postFromObject = [[PAWPost alloc] initWithPFObject:object];
        if ([post equalToPost:postFromObject]) {
            // We found the object, scroll to the cell position where this object is.
            NSUInteger index = [[self objects] indexOfObject:object];

            NSIndexPath *indexPath = [NSIndexPath indexPathForRow:index inSection:kTableViewMainSection];
            [self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionMiddle animated:YES];
            [self.tableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionNone];

            return;
        }
    }

    // Don't scroll for posts outside the search radius.
    if ([post.title compare:kWallCantViewPost] != NSOrderedSame) {
        // We couldn't find the post, so scroll down to the load more cell.
        NSUInteger rows = [self.tableView numberOfRowsInSection:kTableViewMainSection];
        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:(rows - 1) inSection:kTableViewMainSection];
        [self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];
        [self.tableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
        [self.tableView deselectRowAtIndexPath:indexPath animated:YES];
    }
}

- (void)unhighlightCellForPost:(PAWPost *)post {
    // Deselect the post's row.
    for (PFObject *object in [self objects]) {
        PAWPost *postFromObject = [[PAWPost alloc] initWithPFObject:object];
        if ([post equalToPost:postFromObject]) {
            NSUInteger index = [[self objects] indexOfObject:object];
            NSIndexPath *indexPath = [NSIndexPath indexPathForRow:index inSection:0];
            [self.tableView deselectRowAtIndexPath:indexPath animated:YES];

            return;
        }
    }
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // call super because we're a custom subclass.
    [super tableView:tableView didSelectRowAtIndexPath:indexPath];

    [tableView deselectRowAtIndexPath:indexPath animated:YES];

    // highlight annotation pin on map - my problem is here ????

    NSLog(@"tap row --> %i", indexPath.row); //******1*****
    NSLog(@"annotation count --> %i", [self.objects count]); //*****2*****
    UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
    UILabel *textLabel = (UILabel*) [selectedCell.contentView viewWithTag:kPAWCellTextLabelTag];
    NSLog(@"textlabel at the table row tapped --> %@", textLabel.text); //*****3*****


    for (NSInteger i = 0; i < [self.objects count]; i++) {

        PFObject *object = [self.objects objectAtIndex:i];
        PAWPost *postFromObject = [[PAWPost alloc] initWithPFObject:object];
        NSString *text = postFromObject.title;
        NSLog(@"text retrieved from PAWPost --> %@", text); //*****4*****

        if ([text isEqualToString:textLabel.text]) {
            NSLog(@"found matching at %i", i); //*****5*****
            [wallViewController.mapView selectAnnotation:[[wallViewController.mapView annotations] objectAtIndex:i] animated:YES];
            NSLog(@"wallViewController --> %@", wallViewController); //*****6*****
            NSLog(@"wallViewController mapView --> %@", wallViewController.mapView); //*****7*****
        }

    }
}

My problem is in the last method (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath in TableViewController.m. For now I have the code as you see, using:

[wallViewController.mapView selectAnnotation:[[wallViewController.mapView annotations] objectAtIndex:i] animated:YES];

But it doesn't seem to work. There must be something wrong here but I don't know what it is.

Here I provided my log output once I tap the first row of the table:

2015-01-28 11:24:31.886 Test[8097:60b] tap row --> 0
2015-01-28 11:24:31.888 Test[8097:60b] annotation count --> 40
2015-01-28 11:24:31.890 Test[8097:60b] textlabel at the table row tapped --> Asddsdtest
2015-01-28 11:24:31.890 Test[8097:60b] text retrieved from PAWPost --> ...(40 texts here)
2015-01-28 11:24:31.897 Test[8097:60b] found matching at 0
2015-01-28 11:24:31.899 Test[8097:60b] wallViewController --> (null)
2015-01-28 11:24:31.900 Test[8097:60b] wallViewController mapView --> (null)

P.S. I found this question but the answer and comments do not seem to provide enough details for beginner like myself.

Additional Info added

PAWPost.h

@interface PAWPost : NSObject <MKAnnotation>

//@protocol MKAnnotation <NSObject>

// Center latitude and longitude of the annotion view.
// The implementation of this property must be KVO compliant.
@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;

// @optional
// Title and subtitle for use by selection UI.
@property (nonatomic, readonly, copy) NSString *title;
@property (nonatomic, readonly, copy) NSString *subtitle;
// @end

// Other properties:
@property (nonatomic, readonly, strong) PFObject *object;
@property (nonatomic, readonly, strong) PFGeoPoint *geopoint;
@property (nonatomic, readonly, strong) PFUser *user;
@property (nonatomic, assign) BOOL animatesDrop;
@property (nonatomic, readonly) MKPinAnnotationColor pinColor;

// Designated initializer.
- (id)initWithCoordinate:(CLLocationCoordinate2D)coordinate andTitle:(NSString   *)title andSubtitle:(NSString *)subtitle;
- (id)initWithPFObject:(PFObject *)object;
- (BOOL)equalToPost:(PAWPost *)aPost;

- (void)setTitleAndSubtitleOutsideDistance:(BOOL)outside;

@end

PAWPost.m

@interface PAWPost ()

// Redefine these properties to make them read/write for internal class accesses and mutations.
@property (nonatomic, assign) CLLocationCoordinate2D coordinate;

@property (nonatomic, copy) NSString *title;
@property (nonatomic, copy) NSString *subtitle;

@property (nonatomic, strong) PFObject *object;
@property (nonatomic, strong) PFGeoPoint *geopoint;
@property (nonatomic, strong) PFUser *user;
@property (nonatomic, assign) MKPinAnnotationColor pinColor;

@end

@implementation PAWPost

- (id)initWithCoordinate:(CLLocationCoordinate2D)aCoordinate andTitle:(NSString *)aTitle andSubtitle:(NSString *)aSubtitle {
    self = [super init];
    if (self) {
        self.coordinate = aCoordinate;
        self.title = aTitle;
        self.subtitle = aSubtitle;
        self.animatesDrop = NO;
    }
    return self;
}

- (id)initWithPFObject:(PFObject *)anObject {
    self.object = anObject;
    self.geopoint = [anObject objectForKey:kPAWParseLocationKey];
    self.user = [anObject objectForKey:kPAWParseUserKey];

    [anObject fetchIfNeeded]; 
    CLLocationCoordinate2D aCoordinate = CLLocationCoordinate2DMake(self.geopoint.latitude, self.geopoint.longitude);
    NSString *aTitle = [anObject objectForKey:kPAWParseTextKey];
    NSString *aSubtitle = [[anObject objectForKey:kPAWParseUserKey] objectForKey:kPAWParseUsernameKey];

    return [self initWithCoordinate:aCoordinate andTitle:aTitle andSubtitle:aSubtitle];
}

- (BOOL)equalToPost:(PAWPost *)aPost {
    if (aPost == nil) {
        return NO;
   }

    if (aPost.object && self.object) {
        // We have a PFObject inside the PAWPost, use that instead.
        if ([aPost.object.objectId compare:self.object.objectId] != NSOrderedSame) {
            return NO;
        }
        return YES;
    } else {
        // Fallback code:

        if ([aPost.title compare:self.title] != NSOrderedSame ||
        [aPost.subtitle compare:self.subtitle] != NSOrderedSame ||
        aPost.coordinate.latitude != self.coordinate.latitude ||
        aPost.coordinate.longitude != self.coordinate.longitude ) {
            return NO;
        }

        return YES;
    }
}

- (void)setTitleAndSubtitleOutsideDistance:(BOOL)outside {
    if (outside) {
        self.subtitle = nil;
        self.title = kPAWWallCantViewPost;
        self.pinColor = MKPinAnnotationColorRed;
    } else {
        self.title = [self.object objectForKey:kPAWParseTextKey];
        //self.subtitle = [[self.object objectForKey:kPAWParseUserKey] objectForKey:kPAWParseUsernameKey];
        self.subtitle = [NSString stringWithFormat:@"@%@",[[self.object objectForKey:kPAWParseUserKey] objectForKey:kPAWParseUsernameKey]];
        self.pinColor = MKPinAnnotationColorGreen;
    }
}

@end

Answer 1

You can use PFObject.objectId to find annotation what you want.

PFObject *selectedObject = [self.objects objectAtIndex:i];

for (id annotation in wallViewController.mapView.annotations)
{
    if ([annotation isKindOfClass:[PAWPost class]])
    {
        PAWPost *post = (PAWPost*)annotation;
        if ([post.object.objectId isEqualToString:selectedObject.objectId])
        {
            [wallViewController.mapView selectAnnotation:annotation  animated:YES];
            break;
        }
    }
}

Answer 2

You can do your annotation as object that support MSAnnotation protocol. So when you select your cell - you'll exactly know what object is behind this action. And in that case you - your annotation will be exactly the object you've selected by tapping on UITableViewCell.

So - your object PAWPost just should support MKAnnotation protocol:

@interface PAWPost : NSObject <MKAnnotation> 
// Interface here
@end

@implementation PAWPost
// ...
- (CLLocationCoordinate2D)coordinate {
    return <#your coordinate here#>;
}
// ...
@end

P.S. You dont need to create new local instance of WallViewController class in didSelectRowAtIndexPath: method. Because at that time your WallViewController will not have MapView. Instead that - create instance of WallViewController before and use pointer to it.