NSSortDescriptors中的块 - 目标C.

Question

我有一个switch创造相关的声明NSSortDescriptor.对于一些NSSortDescriptors我使用的block作为自定义comparator(比较CMTimes).以下代码工作正常,但我想添加一些NSSortDescriptors比较CMTimes.由于block总是相同的是可以创建一个variable来保持,block所以我不需要继续复制和粘贴杂乱的代码.我想它应该是可能的,但我似乎无法让它发挥作用.我非常感谢任何帮助.谢谢!

NSSortDescriptor *sortDescriptor; 

switch (mode) {
    case 1:
        sortDescriptor = [NSSortDescriptor sortDescriptorWithKey: @"startTime" ascending: YES comparator:^(id first, id second){
                    CMTime time1 = [first CMTimeValue];
                    CMTime time2 = [second CMTimeValue];
                    if (CMTIME_COMPARE_INLINE(time1, <, time2)) 
                        return NSOrderedAscending;
                    else if (CMTIME_COMPARE_INLINE(time1, >, time2))
                        return NSOrderedDescending;
                    else
                        return NSOrderedSame;
        }];
        break;
    case 2:
        sortDescriptor = [NSSortDescriptor sortDescriptorWithKey: @"startTime" ascending: NO comparator:^(id first, id second){
                    CMTime time1 = [first CMTimeValue];
                    CMTime time2 = [second CMTimeValue];
                    if (CMTIME_COMPARE_INLINE(time1, <, time2)) 
                        return NSOrderedAscending;
                    else if (CMTIME_COMPARE_INLINE(time1, >, time2))
                        return NSOrderedDescending;
                    else
                        return NSOrderedSame;
        }];
        break;
    case 3:
        sortDescriptor = [NSSortDescriptor sortDescriptorWithKey: @"info" ascending: YES];
        break;
    case 4:       
        sortDescriptor = [NSSortDescriptor sortDescriptorWithKey: @"info" ascending: NO];
        break;
    default:
        break;
}

Answer 1

您可以创建块变量,这样就不必复制和粘贴块代码.

NSComparator comparisonBlock = ^(id first,id second) {
    return NSOrderedAscending;
};
[NSSortDescriptor sortDescriptorWithKey: @"startTime" ascending: YES comparator:comparisonBlock];