How can I pass a parameter into a view in iOS?

UIViewController *theController = [[HelpViewController alloc] initWithNibName:@"HelpView" bundle:nil];
[self.navigationController presentModalViewCont开发者_开发技巧roller:theController animated:TRUE];

Here's my code for showing my view. I know I can use app delegate variables, but it would be neater is I could pass a parameter in somehow, ideally using an enum. Is this possible?

Just create a new init method for your HelpViewController and then call its super init method from there...

In HelpViewController.h

typedef enum
{
    PAGE1,
    PAGE2,
    PAGE3
} HelpPage;

@interface HelpViewController
{
    HelpPage helpPage;
    // ... other ivars
}

// ... other functions and properties

- (id)initWithNibName:(NSString*)nibName bundle:(NSBundle*)nibBundle onPage:(HelpPage)page;

@end

In HelpViewController.m

- (id)initWithNibName:(NSString*)nibName bundle:(NSBundle*)nibBundle onPage:(HelpPage)page
{
    self = [super initWithNibName:nibName bundle:nibBundle];
    if(self == nil)
    {
        return nil;
    }

    // Initialise help page
    helpPage = page;
    // ... and/or do other things that depend on the value of page

    return self;
}

And to call it:

UIViewController *theController = [[HelpViewController alloc] initWithNibName:@"HelpView" bundle:nil onPage:PAGE1];
[self.navigationController presentModalViewController:theController animated:YES];
[theController release];

I generally just have certain variables in my UIView, which I set from the parent view. To pass variables back, I make use of the function:

[[[self.navigationController viewControllers] lastObject] setFoo:foo];

Define a setter for the parameter in HelpViewController and change your code to:

HelpViewController *theController = [[HelpViewController alloc] initWithNibName:@"HelpView" bundle:nil];
[theController setSomeValue:@"fooBar"];
[self.navigationController presentModalViewController:theController animated:YES];