Singleton of UIView subclass

[pavlicky]

Hi there,

I have UIView subclass, which is supposed to be tableHeaderView for UITableViews. Seen the fact I have multiple UITableViews, I want to "share" instance of UIView subclass between them. Therefore I have following shared method:

HeaderView.h

PHP Code:

static HeaderView *sharedHeader = nil;

+ (HeaderView *)sharedInstance {
    
    @synchronized(self) {
        if (sharedHeader == nil) {
            sharedHeader = [[self alloc] initWithFrame:CGRectMake(0, 0, 320, 120)];
        }
    }
    return sharedHeader;
}

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"HeaderView" owner:self options:nil];
        self = [nib objectAtIndex:0];
    }
    return self;
} 


I call sharedInstance in my UITableViewControllers in viewWillAppear methods:

PHP Code:

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    HeaderView *h = [HeaderView sharedInstance];
    self.tableView.tableHeaderView = h;
} 


When the first UITableViewController appears, it works fine. When the second UITableViewController appears it works fine as well. Problem occurs when I go back to the first UITableViewController -> there is only frame of size 320 x 120, but nothing inside the frame! I have tried to NSLog the tableHeaderView and it prints me <HeaderView: 0x5a75080; frame = (0 0; 320 120); autoresize = RM+BM; layer = <CALayer: 0x5a74f20>> which means there is an object. But why the NIB doesn't show up???

[MatthewD]

You shouldn't have a singleton class that extends UIView. A UIView object can only be added to one display hierarchy - add it to one view as a subview, and it will be removed from its other superview just like you witnessed.

[pavlicky]

Originally Posted by MatthewD

You shouldn't have a singleton class that extends UIView. A UIView object can only be added to one display hierarchy - add it to one view as a subview, and it will be removed from its other superview just like you witnessed.

Oh yeah, I can see. Found out other solution. Thank you for your help ;-)

[raghunath]

Originally Posted by pavlicky

Oh yeah, I can see. Found out other solution. Thank you for your help ;-)

Hi pavlicky,
I'm facing the same problem too. Tried to make the subclass of UIView as Singleton, but came across this post and avoided it. How did you achieve the other way? Did you try creating another subclass of UIView and instantiated the singleton class??

i've got a singleton class too with an Array of instances like this

@interface MyControl:UIControl {

   UIButton *red, *green, *blue;
   UISlider  *colorSlider;
   UIView    *palleteView;
} //Buttons and slider will be added into <palleteView>

//Some properties here

@end;


//Singleton Class
#import "MyControl.h"

@interface ColorPallete:NSObject {
   
   NSMutableArray *arrayOfControls;
}//arrayOfControls will be loaded with instances of MyControl class

+(ColorPallete*) sharedColorPallete;

@end

//I'll be sharing the ColorPallete data in other view controllers of my project

//In the View Controller
#import "ColorPallete.h"

@interface MyViewController :UIViewController {

  ColorPallete *colorPallete;
}

@end;

@implementation MyViewController 

- (void) viewDidLoad {

  colorPallete = [ColorPallete sharedColorPallete];

  [self.view addSubView: ?????];
}

@end

The question is how do I load the array of controls residing inside the singleton class ColorPallete into the ViewController?

[pavlicky]

Originally Posted by raghunath

Hi pavlicky,
I'm facing the same problem too. Tried to make the subclass of UIView as Singleton, but came across this post and avoided it. How did you achieve the other way? Did you try creating another subclass of UIView and instantiated the singleton class??

i've got a singleton class too with an Array of instances like this

@interface MyControl:UIControl {

   UIButton *red, *green, *blue;
   UISlider  *colorSlider;
   UIView    *palleteView;
} //Buttons and slider will be added into <palleteView>

//Some properties here

@end;


//Singleton Class
#import "MyControl.h"

@interface ColorPallete:NSObject {
   
   NSMutableArray *arrayOfControls;
}//arrayOfControls will be loaded with instances of MyControl class

+(ColorPallete*) sharedColorPallete;

@end

//I'll be sharing the ColorPallete data in other view controllers of my project

//In the View Controller
#import "ColorPallete.h"

@interface MyViewController :UIViewController {

  ColorPallete *colorPallete;
}

@end;

@implementation MyViewController 

- (void) viewDidLoad {

  colorPallete = [ColorPallete sharedColorPallete];

  [self.view addSubView: ?????];
}

@end

The question is how do I load the array of controls residing inside the singleton class ColorPallete into the ViewController?

You need to have instance of that UIView subclass. As Matthew said:

Originally Posted by MatthewD
You shouldn't have a singleton class that extends UIView. A UIView object can only be added to one display hierarchy