View Controller Lifecycle Management [Xibless Version]

ACViewController.h

@interface ACViewController : UIViewController
{
    UIViewController* _childViewController;
    UIScrollView* _scrollView;
    UIButton* _button;
    int _counter;
    NSString* _text;
    
    CGPoint _lastScrollViewPosition;
}

@property (assign, nonatomic) BOOL isButtonEnabled;

@end

ACViewController.m

#import "ACViewController.h"

@implementation ACViewController


#pragma mark -
#pragma mark Controller Lifecycle

// Called once the view controller is initialized in your code
- (id)init
{
    self = [super init];
    if (self) {
        // Initialize iVars that live and die with your controller
        _counter = 0;
        _lastScrollViewPosition = CGPointMake(0, 0);
        
        // Initialize child view controllers
        _childViewController = [[UIViewController alloc] init];
    }
    return self;
}



#pragma mark -
#pragma mark View Lifecycle

// Called multiple times whenever the view loads to recreate the view without a XIB file.
// This method only needs to be implemented in the root class of you inheritance hierarchy.
- (void)loadView
{
    // Important, don't call [super loadView].
    // See Apple's View Controller Programming Guide (Custom View Controllers) for details.
    UIView* baseView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    self.view = baseView;
}


// Called multiple times whenever the view loads.
- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // Modify the base view
    self.view.frame = CGRectMake(0, 0, 600, 400);
    self.view.backgroundColor = [UIColor redColor];
    
    // Add scrollview
    _scrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];
    [self.view addSubview:_scrollView];
    
    // Restore state of scrollview
    _scrollView.contentOffset = _lastScrollViewPosition;

    // Add button
    _button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    _button.frame = CGRectMake(10, 10, 200, 50);
    [self.view addSubview:_button];
    
    // Add chidlview controller to view hierachy
    // willMoveToParantViewController gets called automatically
    [self addChildViewController:_childViewController];
    [self.view addSubview:_childViewController.view];
    [_childViewController didMoveToParentViewController:self];
    
    // Initialize iVars that life and die with your view
    _text = @"Hello World";
}


// Called multiple times whenever the view is going to appear.
- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:(BOOL)animated];

    _button.enabled = self.isButtonEnabled;
}


// Called on memory warnings.
- (void)didReceiveMemoryWarning
{
    // Check that the view isn't visible at moment
    if ([self isViewLoaded] && [self.view window] == nil)
    {
        // Release all views that you recreate in loadView and viewDidLoad
        // Important: Set self.view to nil only if you created it.
        self.view = nil;
        _scrollView = nil;
        
        // Remove chidlview controller from view hierachy
        // didMoveToParantViewController gets called automatically
        [_childViewController willMoveToParentViewController:nil];
        [_childViewController.view removeFromSuperview];
        [_childViewController removeFromParentViewController];
        
        // Release iVars that live and die with your view;
        _text = nil;
    }

    // Call super at the end of the method
    [super didReceiveMemoryWarning];
}


@end