从 Parse.com 的 CloudCode 接收空数组时 iOS 崩溃

Question

我正在尝试从返回字典的“Parse.com 的云代码”中获取查询。字典包含两个键，“groups”和“invites”，都是数组。

当其中一个key为空数组时，会出现如下错误:

2014-05-23 17:14:03.967 XXX[2267:60b] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[1]' * First throw call stack: (0x2d589f0b 0x37d20ce7 0x2d4c7cff 0x2d4c7ac3 0x1acd5b 0x1acfef 0xddb95 0xdda07 0xedd4d 0x2fdd3d23 0x2fe83057 0x2fdd3d23 0x2fe38e7f 0x2fe38e09 0x2fdb1b73 0x2d555039 0x2d5529c7 0x2d552d13 0x2d4bd769 0x2d4bd54b 0x3242a6d3 0x2fe1c891 0xe3805 0x3821eab7) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

云代码函数如下:

Parse.Cloud.define("GroupsAndInvites",function(request,response){
        var user = request.user;
        //query memberships and invites for the current user
        var membershipQuery = new Parse.Query("Membership").include("group").equalTo("user",user);
        var inviteQuery = new Parse.Query("Invite").include("from").include("group").equalTo("to",user);

        //make promises
        var membershipPromise = membershipQuery.find();
        var invitePromise = inviteQuery.find();

        //call when both queries are done
        Parse.Promise.when(membershipPromise,invitePromise).then(function(memberships,invites){
                //make an array of groups instead of memberships
                var groups = [];
                for(var i=0;i<memberships.length;i++){
                        groups.push(memberships[i].get("group"));
                }
                //return groups and invites
                response.success({
                        "groups":groups,
                        "invites":invites
                });
        });
});

这是我在前端实现的那个功能:

  [PFCloud callFunctionInBackground:@"GroupsAndInvites" withParameters:nil block:^(NSDictionary *dict, NSError *error) {
    if (!error) {
      NSMutableArray *groupsArray = [NSMutableArray array];
      NSMutableArray *invitesArray = [NSMutableArray array];

      for (BVYGroup *group in dict[@"groups"]) {
        [groupsArray addObject:group];
      }

      for (BVYInvite *invite in dict[@"invites"]) {
        [invitesArray addObject:invite];
      }

      if ([strongDelegate respondsToSelector:@selector(groupStream:didFetchGroups:andInvites:)]) {
        [strongDelegate groupStream:self didFetchGroups:groupsArray andInvites:invitesArray];
      }
    } else {
      if ([strongDelegate respondsToSelector:@selector(groupStream:didFailToFetchGroupsWithError:)]) {
        [strongDelegate groupStream:self didFailToFetchGroupsWithError:error];
      }
    }
  }];

错误发生在检索响应时。它没有到达检查错误的 if 语句。

对为什么会发生这种情况有任何见解吗？
提前谢谢你。

Answer 1

您不能将 nil 插入到 Objective-C 集合中。如果您需要在 Objective-C 集合中表示一个 nil 值，请改用 [NSNull null]。