编辑器加载中...是Foundation框架中的一个普通的类，它提供了到嵌套数列的树中特定节点的路径，事实上，它是一个整数阵列，表格视图使用这个去表现在特定章节中的特定行，UITableView用的所有索引路径正好有两个元素，第一个是章节，第二个是行。
NSIndexPath和TableViews
@interfaceNSIndexPath (UITableView) {
}
+(NSIndexPath*)indexPathForRow:(NSUInteger)row inSection:(NSUInteger)section;
@property(nonatomic,readonly)NSUIntegerrow;
@property(nonatomic,readonly)NSUIntegersection;
@end
NSIndexPath是一種特別的資料類別，這是用來表示一個路徑，這個路徑是指到一個從0開始的巢狀集合陣列樹狀結構的某個節點。iPhone OS為UITableView擴充了這個類別（見NSIndexPath UIKit Additions這是用分類擴充），加入了一個用來建立新的NSIndexPath實體的「(NSIndexPath *)indexPathForRow:(NSUInteger)row inSection:(NSUInteger)section」方法和row和section兩個屬性。
原帖：http://blog.163.com/hw707@126/blog/static/68486388201011255624582/
原博文：http://blog.csdn.net/bellajo/article/details/6772556
nsindexpath的compare方法：
compare:
Indicates the depth-first traversal order of the receiving index path and another index path.
- (NSComparisonResult)compare:(NSIndexPath *)indexPath
Parameters
indexPath
Index path to compare.
This value must not be nil. If the value is nil, the behavior is undefined.
Return Value
The depth-first traversal ordering of the receiving index path and indexPath.
NSOrderedAscending: The receiving index path comes before indexPath.
NSOrderedDescending: The receiving index path comes after indexPath.
NSOrderedSame: The receiving index path and indexPath are the same index path.
Availability
Available in Mac OS X v10.4 and later.
Declared In
NSIndexPath.h