oc_数组排序

// 对dataSourceArray按timestamp的顺序进行降序排列 YES升序、NO降序

 NSSortDescriptor *descriptor = [NSSortDescriptor   sortDescriptorWithKey:@"timestamp"  ascending:NO];

 NSArray*descriptors = [NSArray   arrayWithObject: descriptor];

//进行排序

[dataSourceArray  sortUsingDescriptors: descriptors ];

YES升序 NO降序