Question

我必须遗漏一些基本的东西 - 希望有人可以向我指出。

我有两个NSSets。集合A包含40个NSNumber值，集合B包含20个NSNumber值。集合A包含集合B的20个值以及集合未共享的20个其他值。

我想做的是：NSSet * newSet = Set A - Set B，其中新集合仅包含集合B中未包含的集合A中的20个值。虽然我使用'minusSet'，但我的新set始终包含所有40个原始值。我已经记录了每组A和B的内容，以确保它们包含我上面描述的内容。

这是我的代码：

1）创建集合A（包含40个NSNumber）

NSMutableSet *fetchedThreadIds = [NSMutableSet setWithArray:[threadedJsonMessages valueForKey:@"tid"]];

2）创建集合B（包含20个也在集合A中的NSNumber）

NSSet *savedThreads = threadIdsForSavedThreads([fetchedThreadIds allObjects]);

3）尝试从集合A中减去集合B：

[fetchedThreadIds minusSet:savedThreads];

4）将所有剩余的对象添加到新数组中：

threadIdsForMessageFetch = [fetchedThreadIds allObjects];

但是，threadIdsForMessageFetch包含40个对象而不是20个。当我打印每个集合时，我得到：

设置A

{(
2540000000136987400,
2540000000141777055,
2540000000144609986,
2540000000125243232,
2540000000144610000,
2320000003021796109,
2540000000144375484,
2540000000136185765,
2540000000135311778,
2540000000135311816,
2540000000124128112,
2540000000125012438,
2480000001401011569,
2540000000144610015,
2540000000135311744,
2540000000139755359,
2540000000135311848,
2540000000143846308,
2540000000145732667,
2540000000143985955,
2540000000136185740,
2540000000135756434,
2540000000134373148,
2540000000140816249,
2540000000130860748,
2540000000127140093,
2540000000143526120,
2540000000102176392,
2540000000144609962,
2540000000128826163,
2540000000136185694,
2540000000133208691,
2540000000144555891,
2540000000138091838,
2540000000130179358,
2540000000126098342,
2540000000145162237,
2540000000131688927,
2540000000136185715,
2540000000143526101
)}

设置B

{(
2540000000136987400,
2540000000138091838,
2540000000143985955,
2540000000144555891,
2540000000140816249,
2540000000145732667,
2540000000144609986,
2540000000144610000,
2540000000144609962,
2540000000144610015,
2540000000141777055,
2540000000143526101,
2540000000143526120,
2480000001401011569,
2540000000136185694,
2540000000145162237,
2540000000143846308,
2320000003021796109,
2540000000144375484,
2540000000139755359
)}

新数组：

<__NSArrayI 0xc4b8e40>(
2540000000136987400,
2540000000141777055,
2540000000144609986,
2540000000125243232,
2540000000144610000,
2320000003021796109,
2540000000144375484,
2540000000136185765,
2540000000135311778,
2540000000135311816,
2540000000124128112,
2540000000125012438,
2480000001401011569,
2540000000144610015,
2540000000135311744,
2540000000139755359,
2540000000135311848,
2540000000143846308,
2540000000145732667,
2540000000143985955,
2540000000136185740,
2540000000135756434,
2540000000134373148,
2540000000140816249,
2540000000130860748,
2540000000127140093,
2540000000143526120,
2540000000102176392,
2540000000144609962,
2540000000128826163,
2540000000136185694,
2540000000133208691,
2540000000144555891,
2540000000138091838,
2540000000130179358,
2540000000126098342,
2540000000145162237,
2540000000131688927,
2540000000136185715,
2540000000143526101
)

减号调用前A和B的计数如下：

2014-05-14 22:37:00.900 App[35877:60b] fetchedThreadIdsCount = 40
2014-05-14 22:37:00.900 App[35877:60b] savedThreadsCount = 20

Answer 1

我尝试了这个并且它有效，所以我猜测还有其他代码缺失或者NSNumbers真的不一样，只是打印的表示是相同的。

NSMutableSet *fetchedThreadIds = [NSMutableSet setWithObjects:@1, @2, @3, @4, nil];
NSSet *savedThreads = [NSSet setWithObjects:@2, @3, nil];
NSLog(@"fetchedThreadIds: %@", fetchedThreadIds);
NSLog(@"savedThreads: %@", savedThreads);

[fetchedThreadIds minusSet:savedThreads];
NSLog(@"fetchedThreadIds: %@", fetchedThreadIds);
NSArray *threadIdsForMessageFetch = [fetchedThreadIds allObjects];
NSLog(@"threadIdsForMessageFetch: %@", threadIdsForMessageFetch);

NSLog输出：

fetchedThreadIds：{（
      3，
      2，
      1，
      4）}
  savedThreads：{（
      3，
      2）}
  fetchedThreadIds：{（
      1，
      4）}
  threadIdsForMessageFetch：（
      1，
      4）

主要是为格式化而发布的答案。

NSMutableSet设置减号集不起作用

1 个答案: