False Applescript result in Cocoa

I have 3 tracks in iTunes and run this procedure:

   -(IBAction)reloadButtonClick:(id)sender;
    {
        NSAppleScript *script ;
        NSString *source ;
        NSString *result;
        NSDictionary *errorDic ;
        NSAppleEventDescriptor *ed;
            int total;

        source= @"tell application \"iTunes\" to get count of tracks of playlist 1";
        script = [[NSAppleScript alloc] initWithSource:source];
        ed = [script executeAndReturnError:&errorDic];
        if (ed == nil)
        {
            NSAlert *alert = [[NSAlert alloc]init];
            [alert setMessageText:@"Error Occurred"];
            [alert runModal];
            [alert release];
        }
        result = [ed stringValue];
        total = [result intValue]; 

        开发者_JAVA百科NSAlert *alert = [[NSAlert alloc]init];
        [alert setMessageText:[NSString stringWithFormat:@"%d",total]];
        [alert runModal];
        [alert release];
    }

It always returns 0 and error is not occurred. But, if I execute the script inside Script Editor, it returns 3.

Anyone know what is wrong ? Is AppleScript inside cocoa unstable ?

Thanks.

PS: my iTunes version is 8.0.2 (20)

This bit looks suspect; why aren't you using total = [ed intValue]:

    result = [ed stringValue];
    total = [result intValue]; 

I just tried your code in a foundation tool. I changed it a little:

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    NSAppleScript *script ;
    NSString *source ;
    NSString *result;
    NSDictionary *errorDic ;
    NSAppleEventDescriptor *ed;
    int total;

    source= @"tell application \"iTunes\" to get count of tracks of playlist 1";
    script = [[NSAppleScript alloc] initWithSource:source];
    ed = [script executeAndReturnError:&errorDic];
    if (ed == nil)
    {
        NSLog(@"Error Occurred");
    }
    result = [ed stringValue];
    total = [result intValue]; 

    NSLog( @"result: %d", total );

    [pool drain];
    return 0;
}

With iTunes 9.0.2 (on Mac OS X 10.6.2). It worked fine. It gave me the correct result for my first playlist, "Library".