UIAlertView, once the user opens the app. Shown once - iphone

Question

I want a UIAlertView to show, once the user opens the app. It'll ask them for their email address. But i want it to only show once. So when the user re opens the app the uialertview shouldnt pop up. And the UIAlertView will contain 2 buttons within that. 'Dismiss' & 'Yes' .. the dismiss button will continue with the app. But the 'Yes' will take them to another view'.
Thanks :)
Edit:
- (void)viewDidLoad {
[super viewDidLoad];
if (![#"1" isEqualToString:[[NSUserDefaults standardUserDefaults] objectForKey:#"alert"]]) {
[[NSUserDefaults standardUserDefaults] setValue:#"1" forKey:#"alert"];
[[NSUserDefaults standardUserDefaults] synchronize];
UIAlertView *prompt = [[UIAlertView alloc] initWithTitle:#"Enter your email"
message:#"\n\n\n"
delegate:nil
cancelButtonTitle:#"Cancel"
otherButtonTitles:#"Enter", nil];
textField = [[UITextField alloc] initWithFrame:CGRectMake(12.0, 50.0, 260.0, 25.0)];
[textField setBackgroundColor:[UIColor whiteColor]];
[textField setPlaceholder:#"enter email here"];
[prompt addSubview:textField];
[prompt show];
[prompt release];
//[textField becomeFirstResponder];
}
}
Okay this is the code at the moment, im stuck on how the email is going to be sent to be once the user presses enter.

Answer 1

You can use NSUserDefaults to save a boolean between sessions.
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html
// save
[[NSUserDefaults standardUserDefaults] setObject:[NSNumber numberWithBool:true] forKey:#"hasRunBefore"];
// load
[[NSUserDefaults standardUserDefaults] objectForKey:#"hasRunBefore"] boolValue];

Answer 2

You could store the email address in NSUserDefaults (I guess you are already doing it, if you ask for it only the very first time your app starts); each time the app starts, you check if the email address is there (NSUserDefaults); if not, you display the UIAlertView.

Answer 3

First, need to make yourself the delegate for the UIAlertView so you know when the user has pressed Cancel or Enter. So this:
UIAlertView *prompt = [[UIAlertView alloc] initWithTitle:#"Enter your email"
message:#"\n\n\n"
delegate:self
cancelButtonTitle:#"Cancel"
otherButtonTitles:#"Enter", nil];
The delegate callback is this method:
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
Once that's called, you can retrieve the email address from the textField instance you created and added to the alert view.