如何按陣列數排序嵌套NSArrays的NSArray？

Question

我有一個包含嵌套NSArrays的NSArray。我正在尋找一種方法根據嵌套數組的對象數按升序對父數組進行排序。因此，如果[array1 count]是4，[array2 count]是2和[array3 count]是9，我會得到：數組2，數組1，ARRAY3 ...

Answer 1

有一些解決方案，其中之一是：

NSSortDescriptor *sd = [NSSortDescriptor sortDescriptorWithKey:@"@count" 
                ascending:YES]; 
NSArray *sds = [NSArray arrayWithObject:sd]; 
NSArray *sortedArray = [array sortedArrayUsingDescriptors:sds]; 

Answer 2

static NSInteger MONSortObjectsAscendingByCount(id lhs, id rhs, void* ignored) { 
/* error checking omitted */ 
    const NSUInteger lhsCount = [lhs count]; 
    const NSUInteger rhsCount = [rhs count]; 

    if (lhsCount < rhsCount) { 
     return NSOrderedAscending; 
    } 
    else if (lhsCount > rhsCount) { 
     return NSOrderedDescending; 
    } 
    else { 
     return NSOrderedSame; 
    } 
} 

/* use if mutable, and you wnat it sorted in place */ 
- (void)sortUsingFunction:(NSInteger (*)(id, id, void *))compare context:(void *)context; 

/* else use */ 
- (NSArray *)sortedArrayUsingFunction:(NSInteger (*)(id, id, void *))compare context:(void *)context;