initWithNibName 和 loadNibNamed 的区别

UIViewController initWithNibName

这时候是延迟加载

主要代码如下：

ShowViewController * showMessage = [[ShowViewController alloc]
initWithNibName:@"ShowViewController" bundle:nil];
self.showViewController
release];

这时候是延迟加载，这个View上的控件是 nil 的

self.showViewController.show_Topic 

只有到 需要显示时，才会不是 nil

[saveViewController.view removeFromSuperview];
[self.view insertSubview:showViewController.view atIndex:0];

这时候 xib 文件的要求：

NSBundle loadNibNamed

实时加载。

这时候的代码：

NSArray * nib = [[NSBundle mainBundle] loadNibNamed:@"Save3ViewController" 
                                                          owner:self options:nil] ;
self.showViewController = [nib lastObject];

这时候的xib文件

如果用 loadNibNamed 加载 initWithNibName 用到格式的 xib 文件，就会报错误：

setValue:forUndefinedKey
loaded the...nib but the view outlet was not set

loadNibNamed和initWithNibName需要加载的xib文件是不一样的。initWithNibName需要加载的xib文件的File Owner应改是需要加载的类，

而loadNibNamed需要加载的xib文件的File Owner为NSObject。

when using loadNibNamed:owner:options:, the File's Owner should be NSObject, the main view should be your class type, and all outlets should be hooked up to the view, not the File's Owner.

http://stackoverflow.com/questions/46220/iphone-app-crashing-error-question

参考资料：

从xib/nib加载UIViewController/或其子类

iPhone App Crashing - Error Question
http://stackoverflow.com/questions/46220/iphone-app-crashing-error-question