不用segue的viewcontroller跳转

从一个Controller跳转到另一个Controller时，一般有以下2种：
1、利用UINavigationController，调用pushViewController，进行跳转；这种采用压栈和出栈的方式，进行Controller的管理。调用popViewControllerAnimated方法可以返回。

    PickImageViewController *ickImageViewController = [[PickImageViewController alloc] init];
    [self.navigationController pushViewController: ickImageViewController animated:true];
    [ickImageViewController release];


2、利用UIViewController自身的presentModalViewController，进行跳转；调用dismissModalViewControllerAnimated方法可以返回。
    PickImageViewController *ickImageViewController = [[PickImageViewController alloc] init];
    [self presentModalViewController:ickImageViewController animated:YES];
//返回
[self dismissModalViewControllerAnimated:YES];