NSmutableArray InitWithObjects不工作

伙计们,我在向数组添加nsurl和循环它们时遇到了一些问题。以下是我的代码的相关部分:

RSS阅读器AppDelegate.h:

@interface RSS_ReaderAppDelegate : NSObject <UIApplicationDelegate> {

    UIWindow *window;
    UINavigationController *navigationController;

    NSDictionary *RSSFeeds;
    NSMutableArray *RSSFeedURLs;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController;

@property (nonatomic, retain) NSDictionary *RSSFeeds;
@property (nonatomic, retain) NSMutableArray *RSSFeedURLs;

RSS阅读器AppDelegate.m:

@implementation RSS_ReaderAppDelegate

@synthesize window;
@synthesize navigationController;

@synthesize RSSFeeds, RSSFeedURLs;


#pragma mark -
#pragma mark Application lifecycle

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    // Override point for customization after application launch.

    NSURL *url1 = [[NSURL alloc] initWithString:@"http://<some url>"]; //real URL has been hidden
    NSURL *url2 = [[NSURL alloc] initWithString:@"http://<some other url>"]; //real URL has been hidden

    [RSSFeedURLs initWithObjects: url1, url2, nil];

    [url1 release];
    [url2 release];

    for (NSURL *url in RSSFeedURLs) { //jumps right over this for loop
        NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:url];
        XMLParser *parser = [[XMLParser alloc] init];
        [xmlParser setDelegate:parser];
        //Start parsing the XML file.
        BOOL success = [xmlParser parse];

        if(success)
            NSLog(@"No Errors");
        else
            NSLog(@"Error(s) encountered");
    }//for
    // Add the navigation controller's view to the window and display.
    [window addSubview:navigationController.view];
    [window makeKeyAndVisible];

    return YES;
}

所以 [RSSFeedURLs initWithObjects: url1, url2, nil]; 当我运行调试器并键入“po rssfeedsurls”时,它似乎没有实际做任何事情,它报告:“无法访问地址为0x0的内存”,因此从未输入for循环。我不知道为什么会这样,有人能为我解释一下这种情况吗?事先谢谢。