ios - How to restrict a moveable view by Pan gesture -

i have uiimageview moveable via pan gesture.

uipangesturerecognizer *pan = [[uipangesturerecognizer alloc] initwithtarget:self action:@selector(handlepan:)]; [self.photomask addgesturerecognizer:pan]; 

i restrict area can moved on screen. rather user able drag view right side of screen, want restrict margin of sort. how can this?

also, how handled when rotated?

edit ---

#pragma mark - gesture recognizer -(void)handlepan:(uipangesturerecognizer *)gesture {     nslog(@"pan gesture");     gesture.view.center = [gesture locationinview:self.view]; } 

this current method handle pan. need continue move imageview center point , restrict movement when close edge of screen 50 example.

one possible solution in handlepan method, check location of point on screen, , commit change if within bounds wish restrict to.

for ex.

-(void) handlepan:(uigesturerecognizer*)panges{      cgpoint point = [panges locationinview:self.view];      //only allow movement within 100 pixels of right bound of screen     if (point.x < [uiscreen mainscreen].bounds.size.width - 100) {          cgrect newframe = cgrectmake(point.x, point.y, theimageview.frame.size.width, theimageview.frame.size.height);          theimageview.frame = newframe;      }  } 

i believe correctly handle screen rotation

edit

to move image view center of frame, handlepan method this.

-(void)handlepan:(uipangesturerecognizer *)gesture {      cgpoint point = [gesture locationinview:self.view];      //only allow movement within 50 pixels of bounds of screen     //ex. (iphone 5)     cgrect boundsrect = cgrectmake(50, 50, 220, 448);      if (cgrectcontainspoint(boundsrect, point)) {         imgview.center = point;     }        } 

check whether point within desired bounds, , if so, set center of image view frame point.