ios - why does it not zoom? -

new objective c!

im trying make mapview zoom. i've copied code assignment in book, somehow doesn't zoom. shows unzoomed mapview.

any suggestions? see viewcontroller code below.

also - few words on difference of importing header file , @class directive great!?

thanks in advance

#import "trackviewcontroller.h" #import "mainwindowviewcontroller.h" #import <mapkit/mapkit.h>    @class mainwindowviewcontroller; @implementation trackviewcontroller  - (id) initwithnibname:(nsstring *)nibnameornil bundle:(nsbundle *)nibbundleornil  {         self=[super initwithnibname:nibnameornil bundle:nibbundleornil];  if(self) {     locationmanager = [[cllocationmanager alloc]init];     [locationmanager setdelegate:self];     [locationmanager setdesiredaccuracy:kcllocationaccuracybest]; }     return self; }  -(ibaction) back:(id)sender {     [self dismissviewcontrolleranimated:yes completion:nil]; }  -(void) findlocation; {     [locationmanager startupdatinglocation]; }  -(void) foundlocation:(cllocation *)loc {     cllocationcoordinate2d coord = [loc coordinate];     mkcoordinateregion region =  mkcoordinateregionmakewithdistance(coord, 100, 100);     [worldview setregion:region];     [locationmanager stopupdatinglocation]; }  -(void)viewdidload {     [worldview setshowsuserlocation:yes];     [worldview setmaptype:mkmaptypehybrid];     }  -(void)dealloc {     [locationmanager setdelegate:nil]; }  - (void) locationmanager:(cllocationmanager *) manager  didupdatetolocation:(cllocation *)newlocation         fromlocation:(cllocation *)oldlocation {  nstimeinterval t = [[newlocation timestamp] timeintervalsincenow]; if(t<180){     return; }     [self foundlocation:newlocation]; }  -(void)locationmanager:(cllocationmanager *)manager   didfailwitherror:(nserror *)error {     nslog(@"could not find location: %@", error); }  @end 

the thing notice change setregion line to:

[worldview setregion:region animated:yes];//instead of setregion 

-the setregion: documentation states:

the area displayed map view

-while setregion:animated: documentation states:

changes visible region , optionally animates change

otherwise, recommend printing out cllocationcoordinate2d object , ensuring valid.