Unable to show child view (iOS view container) - ios

Question

In my iOS application, I have a main View Controller with three buttons, which work like a tab bar: when I click one of the buttons, a new view controller is invoked.
I tried to implement this via container view containers, so I tried following this guide (http://www.thinkandbuild.it/working-with-custom-container-view-controllers/) and invoke the presentDetailController method in the viewDidLoad of the main controller.
Actually, no views are showed: someone can help me figuring out why? Thanks.
ViewController.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#property (weak, nonatomic) IBOutlet UIButton *btnOne;
#property (weak, nonatomic) IBOutlet UIButton *btnTwo;
#property (weak, nonatomic) IBOutlet UIButton *btnThree;
#property (weak, nonatomic) IBOutlet UIView *detailView;
- (IBAction)click:(id)sender;
#end
ViewController.m
#import "ViewController.h"
#import "FirstViewController.h"
#interface ViewController ()
#property UIViewController *currentDetailViewController;
#end
#implementation ViewController
#synthesize btnOne, btnTwo, btnThree;
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
FirstViewController *fvc = [[FirstViewController alloc]initWithString:#"I'm the first Controller!"];
[self presentDetailController:fvc];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)click:(id)sender
{
// button selection stuff
[self addDetailController:sender];
}
- (void)presentDetailController:(UIViewController*)detailVC{
//0. Remove the current Detail View Controller showed
if(self.currentDetailViewController){
[self removeCurrentDetailViewController];
}
//1. Add the detail controller as child of the container
[self addChildViewController:detailVC];
//2. Define the detail controller's view size
detailVC.view.frame = [self frameForDetailController];
//3. Add the Detail controller's view to the Container's detail view and save a reference to the detail View Controller
[self.detailView addSubview:detailVC.view];
self.currentDetailViewController = detailVC;
//4. Complete the add flow calling the function didMoveToParentViewController
[detailVC didMoveToParentViewController:self];
}
- (void)removeCurrentDetailViewController{
//1. Call the willMoveToParentViewController with nil
// This is the last method where your detailViewController can perform some operations before neing removed
[self.currentDetailViewController willMoveToParentViewController:nil];
//2. Remove the DetailViewController's view from the Container
[self.currentDetailViewController.view removeFromSuperview];
//3. Update the hierarchy"
// Automatically the method didMoveToParentViewController: will be called on the detailViewController)
[self.currentDetailViewController removeFromParentViewController];
}
- (CGRect)frameForDetailController{
// newFrame's height should be currentFrame's height minus buttons' height
CGRect detailFrame = CGRectMake(0, 0, self.detailView.bounds.size.width, self.detailView.bounds.size.height-self.btnOne.frame.size.height);
return detailFrame;
}
- (void)addDetailController:(id)sender {
FirstViewController *detailVC = [[FirstViewController alloc]initWithString:#"First button clicked"];
[self presentDetailController:detailVC];
}
#end
FirstViewController.h
#import <UIKit/UIKit.h>
#class ViewController;
#interface FirstViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *label;
#property (weak, nonatomic) IBOutlet UIButton *btnOne;
#property (weak, nonatomic) IBOutlet UIButton *btnTwo;
#property (weak, nonatomic) IBOutlet UIButton *btnThree;
- (id)initWithString:(NSString*)string;
#end
FirstViewController.m
#import "FirstViewController.h"
#interface FirstViewController (){
NSString *text;
}
#end
#implementation FirstViewController
- (id)initWithString:(NSString*)string {
self = [super init];
if(self){
text = string;
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.label.text = text;
}
#end

Answer 1

As part of creating FirstViewController, you are calling [super init] which produces a bare UIViewController. From your diagram, it seems as if you want to load a FirstViewController from your storyboard instead.
I suggest a sequence where you create your controller using instantiateViewControllerWithIdentifier:, then set a string property in the controller that you want to use as the label, and finally assign the string to the label when the controller's view loads.