nib文件的注册及加载

1，注册

[(UIView *)view registerNib:[UINib nibWithNibName:(NSString *)nibName bundle:(NSBundle *)bundle] forCellReuseIdentifier:(NSString *)identifier];

2，加载

cell = [[[NSBundle mainBundle] loadNibNamed:nibName owner:self options:nil] lastObject];

自定义的空间一般采用加载nib文件的形式创建，用new创建没有定义好的布局。

其中，- (NSArray *)loadNibNamed:(NSString *)name
                    owner:(id)owner

                  options:(NSDictionary *)options

的作用是Unarchives the contents of a nib file located in the receiver's bundle.

3，NSBundle的作用

作用：NSBundle用来管理项目中的资源文件，NSBundle实体可以定位项目中用到的资源，动态加载或者卸载可执行代码，起到辅助定位的功能。个人觉得英文版更能解释这个概念。

NSBundle : An NSBundle object represents a location in the file system that groups code and resources that can be used in a program. NSBundle objects locate program resources, dynamically load and unload executable code, and assist in localization. 

若为nil，则默认为mainBunble。