UIScrollView referenced both by UIViewController's 'view' property and by an outlet - iphone

Question

I'm about to add a UIScrollView to my iPhone project and before I implement this functionality I wanted to check if my approach is the right one or if I could be violating some best practice I'm not aware of.
The tutorials I've seen generally involve adding a UIScrollView to an existing UIView and they work from there. However, I was wondering if I could spare the UIView altogether and just add the UIScrollView as the only top-level object in my nib file.
My sample project uses Xcode's View-based Application template:
Project navigator http://img542.imageshack.us/img542/5364/projectnavigator.png
I deleted the UIView top-level object from the original MySampleViewController.xib file and replaced it by adding a UIScrollView object:
Nib placeholders http://img526.imageshack.us/img526/7709/placeholderobjects.png
Now my nib file only shows this object in the canvas:
Canvas http://img233.imageshack.us/img233/4063/scrollview.png
Then I created the link from the UIViewController's view outlet to the UIScrollView.
Now, if I wanted to programmatically manipulate the contents of the UIScrollView I can use this code:
- (void)viewDidLoad {
[super viewDidLoad];
NSArray *colors = [NSArray arrayWithObjects:[UIColor redColor], [UIColor greenColor], [UIColor blueColor], nil];
// Solution B: With the following line we avoid creating an extra outlet linking to the UIScrollView top-level object in the nib file
UIScrollView *scrollView = (UIScrollView *)self.view;
for (int i = 0; i < colors.count; i++) {
CGRect frame;
//frame.origin.x = self.scroller.frame.size.width * i; // Solution A: scroller is an IBOutlet UIScrollView *scroller;
frame.origin.x = scrollView.frame.size.width * i; // Solution B
frame.origin.y = 0;
//frame.size = self.scroller.frame.size; // Solution A
frame.size = scrollView.frame.size; // Solution B
UIView *subView = [[UIView alloc] initWithFrame:frame];
subView.backgroundColor = [colors objectAtIndex:i];
//[self.scroller addSubview:subView]; // Solution A
[self.view addSubview:subView]; // Solution B
[subView release];
}
//self.scroller.contentSize = CGSizeMake(self.scroller.frame.size.width * colors.count, self.scroller.frame.size.height); // Solution A
scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * colors.count, scrollView.frame.size.height); // Solution B
}
In order to implement Solution A the scroller outlet must be linked to the nib's UIScrollView as well, and the Connections Inspector looks like this:
Connections Inspector http://img228.imageshack.us/img228/8397/connectionsj.png
Solution A requires an outlet and this means having two connections to the UIScrollView: the UIViewController's own view outlet and MySampleViewController's scroller outlet. Is it legal and/or recommended to have two outlets pointing to the same view?
Solution B only involves UIViewController's view outlet linking to the view, and using this line:
UIScrollView *scrollView = (UIScrollView *)self.view;
My questions:
Do I incur in some sort of violation of Apple's design guidelines by using one of these two solutions?
Should I stick to the UIScrollView within a UIView solution?
Is there any other way to implement this?
Thanks!
P.S. Sorry for the syntax highlight, SO didn't recognize the use of the 'objective-c' tag

Answer 1

No I think you are fine either way.
I would, I don't think a UIView has any significant cost, plus what if you want to add a page control? and you don't have to cast the controller's view to a UIScrollView every time you need it.
Looks like you have it under control to me.
Solution A requires an outlet and this means having two connections to the UIScrollView: the UIViewController's own view outlet and MySampleViewController's scroller outlet. Is it legal and/or recommended to have two outlets pointing to the same view?
It standard to have IBOutlets to any view defined in your .nib that you want to access directly from your view controller.
If you don't want two outlets you could give the scroll view a tag then find it like so:
UIScrollView *myScrollView = (UIScrollView *)[self.view viewWithTag:1]
Then you only have the view as an outlet, but I would just add the extra outlet. Just make sure you set them to nil in your viewDidUnload.
Also you don't have to retain the scroll view (if you are even still using retain/release). Since the scroll view is inside your view controller's view it keeps a reference so you can have your scrollview's property by assign or week if your using ARC.
Hope that helps.