Question

I’m developing on iOS and I’m building my views programmatically. I noticed that when I try to access variables that have to be changed in my view from the view controller they are null. I’ll post both the view and its view controller:

RootViewController.h

 #import <UIKit/UIKit.h>

@class RootView;

@interface RootViewController : UIViewController {
    RootView *rootView;
}

@property (nonatomic,retain) RootView *rootView;


@end

RootViewController.m

    #import "RootViewController.h"
#import "RootView.h"

@implementation RootViewController

@synthesize rootView;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}



- (void)dealloc
{
    [rootView release];
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)loadView{
    RootView *rootV = [[RootView alloc] initWithFrame:CGRectMake(10, 10, 100, 50)];
    rootV.rootViewController = self;
    self.view = rootV;
    [rootV release];
}

- (void)viewDidLoad{
    NSLog(@"TEXT: %@",self.rootView.label.text);
    self.rootView.label.text=@"HELLO!";
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    [self setRootView:nil];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

RootView.h

   #import <UIKit/UIKit.h>

@class RootViewController;

@interface RootView : UIView {
    RootViewController *rootViewController;
    UILabel *label;
}

@property (nonatomic,assign) RootViewController *rootViewController;
@property (nonatomic,retain) UILabel *label;


@end

RootView.m

   #import "RootView.h"
#import "RootViewController.h"

@implementation RootView
@synthesize rootViewController;
@synthesize label;

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        //Create the label
        UILabel *testLabel = [[UILabel alloc] initWithFrame:CGRectMake(100, 100,100, 50)];
        //Set the font bold 
        testLabel.font = [UIFont boldSystemFontOfSize:20.0];
        //Set the backgroundcolor of the label to transparent
        testLabel.backgroundColor = [UIColor clearColor];
        //Set the text alignment of the text label to left
        testLabel.textAlignment = UITextAlignmentLeft;
        //Set the text color of the text label to black
        testLabel.textColor = [UIColor blackColor];
        testLabel.text = @"01:30";

        self.label = testLabel;

        [self addSubview:label];
        [testLabel release];
    }
    return self;
}


- (void)dealloc
{
    [label release];
    rootViewController = nil;
    [super dealloc];
}

@end

I changed the code but it seems not working…..

Ok solved I forgot this line “self.rootView = rootV;”

Answer 1

Your view doesn’t find out what its controller is until after its -initRootView method returns, but you’re trying to use the controller from within that method.

That said, it would be much better if you followed the usual Cocoa Touch pattern for a view controller creating its view. View controllers are supposed to create their views lazily, which is to say that they defer view creation and initialization until the -loadView method is called. You can override -loadView to create your view, and also override -viewDidLoad to do any setup work that needs to be done after the view is created.

Also, it’s generally not advisable for a view to know about its controller. The controller should tell the view what to do, not the other way around. If you need the view to send some information to the controller, you usually provide the controller to the view as the view’s delegate. But if you just need the view controller to be able to find some subview, like your label, it’s probably a good idea to either provide some accessors in the container view for that (so that the view controller can just say something like self.view.label.text = @"some text";. Another options is to set the subview’s tag property to some unique value and have the controller use that to find the subview.