按日期属性

Question

我有一个NSMutableArray，它有一个内部NSMutableArray，我想用内部NSMutableArray中的日期属性对其排序（对外部项进行排序）。

The array looks like this
[
  {
     messages : [
     { 
     date
     },
     ..... etc
     ]
  },
..... etc
]

以下代码是我尝试抛出异常

NSSortDescriptor *sdSortDate = [NSSortDescriptor sortDescriptorWithKey:@"messages.@lastObject.date" ascending:YES];
events = [NSMutableArray arrayWithArray:[events sortedArrayUsingDescriptors:@[sdSortDate]]];

示例

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '[<__NSArrayM 0x604000654670> valueForKeyPath:]: this class does not implement the lastObject operation.'

关于我如何做到这一点的任何想法？

Answer 1

您应该使用messages.date.@lastObject代替messages.@lastObject.date。请尝试以下代码

NSSortDescriptor *sdSortDate = [NSSortDescriptor sortDescriptorWithKey:@"messages.date.@lastObject" ascending:YES];
events = [NSMutableArray arrayWithArray:[events sortedArrayUsingDescriptors:@[sdSortDate]]];