加载storyboard和xib文件

    // 加载storyboard
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Two" bundle:nil];
    
    // 创建storyboard里面灰色的控制器
　　　//找到shtoryboard里面设置的初始控制器
    //    UIViewController *vc = [storyboard instantiateInitialViewController];
　　
　　// 从storyboard里面找出绑定标识的控制器
    MJTwoViewController *vc = [storyboard instantiateViewControllerWithIdentifier:@"pink"];
    self.window.rootViewController = vc;

//nib文件初始化
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
//加载所有xib文件

NSArray* objects = [[NSBundle mainBundle] loadNibNamed:nibName owner:self options:nil]

//加载指定xib文件

ContactsTableViewCell  *cell = [[[NSBundle mainBundle]loadNibNamed:@"ContactsTableViewCell" owner:nil options:nil] objectAtIndex:0]