Question

我正在查询解析时的关系数据，我希望这些对象按照它们创建日期的顺序返回。我之前已经使用过这种方法，但是无法使用关系数据获得有序查询。查询返回是随机顺序。提前致谢！这是我的代码：

    PFQuery *postQuery = [PFQuery queryWithClassName:@"Post"];
    [roomQuery whereKey:@"name" equalTo:self.postName];

    NSError *error;
    //done on main thread to have data for next query
    NSArray *results = [postQuery findObjects:&error];

    PFObject *post;

    if ([results count]) {
        post = [results objectAtIndex:0];
        NSLog(@"results were found");
    } else {
        NSLog(@"results were not found");
    }

    PFRelation *commentsRelation = [@"Comments"];
    [commentsRelation.query orderByAscending:@"createdAt"];
    [commentsRelation.query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
        if (error) {
            NSLog(@"Error Fetching Comments: %@", error);
        } else {
            NSArray *comments = objects; 
     }

Answer 1

我对你的代码感到有些困惑，

你创建了一个“postQuery”，然后调用它，但从不使用它的任何数据。
还有一个似乎从未被分配或使用的roomQuery。
您要按名称查询特定帖子。你在控制它的名字吗？如果没有，你应该使用id's
什么是PFRelation commentsRelation = [@“Comments”];

可能因为它只是一个片段，这些东西在别处处理;但是，对于我的回答，我假设你的“评论”字段是一个“评论”类对象的数组。

选项1：

PFQuery * postQuery = [PFQuery queryWithClassName:@"Post"];
[postQuery whereKey:@"name" equalTo:self.postName]; 
// again, possibly an id field would be more reliable
// [postQuery whereKey:@"objectId" equalTo:self.postId];
[postQuery includeKey:@"Comments"];
PFObject * post = [postQuery getFirstObject];// no need to download all if you just want object at [0]
// this will contain your post and all of it's comments with only one api call
// unfortunately, it's not sorted, so you would have to run a sort.
NSArray * comments =  [post[@"Comments"] sortedArrayUsingComparator: ^(id obj1, id obj2) {
    return [obj1[@"createdAt" compare: obj2[@"createdAt"];
}];

选项2：

也许更好的选择是重新设计数据结构，而不是将评论与帖子相关联，您可以将帖子与评论相关联（如在解析文档中）

PFQuery * postQuery = [PFQuery queryWithClassName:@"Post"];
[postQuery whereKey:@"name" equalTo:self.postName]; 
// again, possibly an id field would be more reliable
// [postQuery whereKey:@"objectId" equalTo:self.postId];

PFQuery * commentQuery = [PFQuery queryWithClassName:@"Comment"];
[commentsQuery whereKey:@"parent" matchesQuery:postQuery]; // when creating a comment, set your post as its parent
[commentsQuery addOrderDescending:@"createdAt"]
[commentQuery findObjectsInBackgroundWithBlock:^(NSArray *comments, NSError *error) {
    // comments now contains the comments for myPost
}];

上述两种解决方案都避免了额外的不必要的api呼叫（毕竟根据呼叫解析费用！）。

对Parse关系数据的查询不会使用orderedByAscending返回

1 个答案: