Working with a container view - objective-c

Question

This is my situation. I have a viewController. With at the top three buttons and below the buttons a containerview. When you push a button, the container view should change.
This is what I have done in storyboard.
Dragged a view controller into my storyboard. added 3 buttons and a containerview into it.
This view controller is off class viewController
Dragged a second viewcontroller into it. And controlled dragged from the containerView to this view controller. and selected embed segue.
Now in code I do the following for controller viewController
-(IBAction)chooseFirstController:(id)sender {
[self.childViewControllers.lastObject switchToFirst];
}
-(IBAction)chooseSecondController:(id)sender {
[self.childViewControllers.lastObject switchToSecond];
}
-(IBAction)chooseThirdController:(id)sender {
[self.childViewControllers.lastObject switchToThird];
}
And for my containerController.h I do the following.
#interface ContainerViewController : ViewController
#property (nonatomic,strong) FirstController *cont1;
#property (nonatomic,strong) SecondController *cont2;
#property (nonatomic,strong) ThirdController *cont3;
#property (nonatomic,strong) ContainerViewController *currentController;
And in my container.m
- (void)viewDidLoad
{
[super viewDidLoad];
self.cont1 = [[FirstController alloc]initWithNibName:#"FirstController" bundle:nil];
self.cont2 = [[SecondController alloc]initWithNibName:#"SecondController" bundle:nil];
self.cont3 = [[ThirdController alloc]initWithNibName:#"ThirdViewController" bundle:nil];
[self addChildViewController:self.cont1];
self.currentController = self.cont1;
[self.view addSubview:self.cont1.view];
}
-(void)switchToFirst {
if (self.currentController != self.cont1) {
[self addChildViewController:self.cont1];
[self moveToNewController:self.cont1];
}
}
-(void)switchToSecond {
if (self.currentController != self.cont2) {
[self addChildViewController:self.cont2];
[self moveToNewController:self.cont2];
}
}
-(void)switchToThird {
if (self.currentController != self.cont3) {
[self addChildViewController:self.cont3];
[self moveToNewController:self.cont3];
}
}
-(void)moveToNewController:(id) newController {
[self.currentController willMoveToParentViewController:nil];
[self transitionFromViewController:self.currentController toViewController:newController duration:.6 options:UIViewAnimationOptionTransitionFlipFromLeft animations:^{}
completion:^(BOOL finished) {
[self.currentController removeFromParentViewController];
[newController didMoveToParentViewController:self];
self.currentController = newController;
}];
}
But I keep getting error "No known instance method for selector switchtoFirst" in my IBActions.
Can anybody help me?
Thanks in advance.

Answer 1

I would guess that lastObject is returning a UIViewController and doesn't know it's a ContainerViewController - hence doesn't know about the switchtoFirst method.
Try something like:
-(IBAction)chooseFirstController:(id)sender {
UIViewController *vc = self.childViewControllers.lastObject;
if([vc isKindOfClass:[ContainerViewController class]]) {
ContainerViewController *containerVC = (ContainerViewController *)vc;
[containerVC switchtoFirst];
}
}