cocoa - Animating NSTabView Views -

i trying animate each view of nstabview slide in when view selected. have working in fashion, animates first time select new tab view. after not see animation when switching tab views, although can see the function fired every time.?

override func tabview(tabview: nstabview, didselecttabviewitem tabviewitem: nstabviewitem) {     tabviewitem.view!.setframeorigin(nspoint(x: tabviewitem.view!.frame.origin.x + 300, y: tabviewitem.view!.frame.origin.y))     tabviewitem.view!.animator().setframeorigin(nspoint(x: tabviewitem.view!.frame.origin.x - 300, y: tabviewitem.view!.frame.origin.y))     // can see fires every time switch tab views animation works fist time } 

i have changed little solve first time problem. define integer store previous tab index in delegate.

- (void)tabview:(nstabview *)tabview didselecttabviewitem:(nstabviewitem *)tabviewitem{      cabasicanimation *controlposanim = [cabasicanimation animationwithkeypath:@"position"];     if (prevtabviewindex>[tabview indexoftabviewitem:tabviewitem]) {         [controlposanim setfromvalue:[nsvalue valuewithpoint:cgpointmake(tabviewitem.view.frame.origin.x - 500,tabviewitem.view.frame.origin.y)]];      } else {         [controlposanim setfromvalue:[nsvalue valuewithpoint:cgpointmake(tabviewitem.view.frame.origin.x + 500,tabviewitem.view.frame.origin.y)]];     }      [controlposanim settovalue:[nsvalue valuewithpoint:cgpointmake(tabviewitem.view.frame.origin.x,tabviewitem.view.frame.origin.y)]];     [[tabviewitem.view layer] addanimation:controlposanim forkey:@"controlviewposition"];     [tabviewitem.view setanimations:[nsdictionary dictionarywithobjectsandkeys:controlposanim, @"frameorigin", nil]];      [tabviewitem.view.animator setframeorigin : cgpointmake(tabviewitem.view.frame.origin.x,tabviewitem.view.frame.origin.y)];      prevtabviewindex = [tabview indexoftabviewitem:tabviewitem]; }