How to get an url from textfield and use it in the application?

I have been working on a easy RSS reader for my own. I am new to Objective-C so I am stuck at one point. There is a add button on the navigation bar of the application which opens a uialertview with a textfield where the user gonna input the url of the rss feed. The application has a predefined rss feed address in its source code. I am writing my code examples below:

- (void)viewDidLoad {    [super viewDidLoad];        self.feeds = [NSArray arrayWithObjects:@"http://www.formula1.com/rss/news/latest.rss",                  nil];

feeds is the predefined array which has the address of the feed. I tried that code below to get the text but it didnt work. Also how the application gonna take that url from textfield and replace with the predefined one?

- (void) myAlertView:(UIAlertView *)alert clickedButtonAtIndex:(NSInteger)buttonIndex{    if (buttonIndex == 1)    { // Ok pushed        //[data addObject:myTextField.text];    }