Question

我有一个活动类，一个主题类和一个照片类。如果有跟随活动，我需要找出用户遵循的主题，然后用该主题标记哪些照片。这是我的代码：

PFQuery *themeQuery = [PFQuery queryWithClassName:@"Occasion"];
PFQuery *followingActivitiesQuery = [PFQuery queryWithClassName:kPAPActivityClassKey];

[followingActivitiesQuery whereKey:kPAPActivityFromUserKey equalTo:[PFUser currentUser]]; 
[followingActivitiesQuery whereKey:@"type" equalTo:@"followtheme"]; 
[followingActivitiesQuery includeKey:@"themePointer"];

NSArray *objects = [followingActivitiesQuery findObjects];

for (PFObject *object in objects) {
   PFObject *tobject = object[@"themePointer"];
   NSString *themename = [tobject valueForKey:@"name"];
   [themeQuery whereKey:@"name" equalTo: themename];
}

PFQuery *photosFromFollowedThemeQuery = [PFQuery queryWithClassName:self.parseClassName];
[photosFromFollowedThemeQuery whereKey:@"themeRelation" matchesQuery:themeQuery];

此代码有效，但findobjects是一个阻塞调用，所以我的应用程序在等待时会挂起一点。如何重写此查询？

Answer 1

不使用findObjects，而是使用异步执行的findObjectsInBackgroundWithBlock:并且不阻止主线程。

所以你的代码看起来像这样：

PFQuery *themeQuery = [PFQuery queryWithClassName:@"Occasion"];
// ... add filters ...
[themeQuery findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
    NSLog(@"Results: %@", results);
}];

[更新] 以下是您查询的一些其他示例代码，我在脑海中编译了这些代码，因此可能需要进行一些调整。

PFQuery *followingActivitiesQuery = [PFQuery queryWithClassName:kPAPActivityClassKey];
[followingActivitiesQuery whereKey:kPAPActivityFromUserKey equalTo:[PFUser currentUser]]; 
[followingActivitiesQuery whereKey:@"type" equalTo:@"followtheme"]; 
[followingActivitiesQuery includeKey:@"themePointer"];
[followingActivitiesQuery findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
    PFQuery *themeQuery = [PFQuery queryWithClassName:@"Occasion"];
    for (PFObject *object in results) {
       PFObject *tobject = object[@"themePointer"];
       NSString *themename = [tobject valueForKey:@"name"];
       [themeQuery whereKey:@"name" equalTo: themename];
    }

    PFQuery *photosFromFollowedThemeQuery = [PFQuery queryWithClassName:self.parseClassName];
    [photosFromFollowedThemeQuery whereKey:@"themeRelation" matchesQuery:themeQuery];
    [photosFromFollowedThemeQuery findObjectsInBackgroundWithBlock:^(NSArray *finalResults, NSError *finalError) {
        // Do something with the final results
    }];
}];

在解析的查询中阻止调用

1 个答案: