NSMutableArray 输出错误数据

Question

我使用Parse.com 作为我的应用程序的后端。

每个用户都可以访问PFObjects 的列表。如果当前用户想要“收藏”一个对象，我想将其从当前用户的主列表中删除。

下面是我的代码，运行在ObjectsDidLoad。

如果我注销下面的代码，PFRelation 中的 PFObject 将被删除，但在我的 UITableView 中，NSMutableArray 中的最后一项将被删除。

我在错误的位置运行它吗？

可能少了一个步骤？

谢谢！

代码如下：

- (void)objectsDidLoad:(NSError *)error {
    [super objectsDidLoad:error];

    PFRelation *relation = [[PFUser currentUser] relationForKey:@"myRelation"];
    PFQuery *relationQuery = relation.query;
    [relationQuery findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {

        NSMutableArray *arrayToShow = [NSMutableArray arrayWithArray:self.objects];

        for (PFObject *object1 in self.objects) {
            for (PFObject *object2 in results) {
                if ([[object1 objectForKey:@"title"] isEqualToString:[object2 objectForKey:@"title"]]) {
                    [arrayToShow removeObject:object1];
                }
            }
        }

        self.objectsToShowArray = [NSMutableArray arrayWithArray:arrayToShow];

        [self.tableView reloadData];
    }];
}

更多说明：

表 A 或主表加载 Parse 类中的所有对象。每个用户都可以访问它。

用户选择一个对象以转到另一个视图控制器，并且可以点击一个按钮将其添加到另一个 Parse 类。这也会创建一个 PFRelation。

因此，如果用户将对象“xyz”添加到 Parse Class B 和 Table B，我希望该对象不会为他们显示在 Table A 中（尽管它必须保留在 Parse Class A 中，因为每个用户都可以访问它） .

所以，我想查询 Parse Class A，查询 PFRelation，并从表 A 上显示的数组中删除匹配的对象。

这是我的 queryForTable 方法：

- (PFQuery *)queryForTable {
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];
    [query orderByAscending:@"title"];

    // **********************************
    // PFRelation
    PFRelation *relation = [[PFUser currentUser] relationForKey:@"myRelation"];
    PFQuery *relationQuery = relation.query;
    [relationQuery findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {

        NSMutableArray *arrayToShow = [NSMutableArray arrayWithArray:self.objects];

        for (PFObject *object1 in self.objects) {
            for (PFObject *object2 in results) {
                if ([[object1 objectForKey:@"title"] isEqualToString:[object2 objectForKey:@"title"]]) {
                    [arrayToShow removeObject:object1];
                }
            }
        }
        self.objectsToShowArray = [NSMutableArray arrayWithArray:arrayToShow];
        [self.tableView reloadData];
    }];
    // **********************************

    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

    NSObject * object = [prefs objectForKey:@"category"];
    if(object != nil){
        //object is there
        self.categoryString = [NSString stringWithFormat:@"%@", object];

        [query whereKey:@"category" equalTo:self.categoryString];
    }

    // A pull-to-refresh should always trigger a network request.
    [query setCachePolicy:kPFCachePolicyNetworkOnly];

    // If no objects are loaded in memory, we look to the cache first to fill the table
    // and then subsequently do a query against the network.
    //
    // If there is no network connection, we will hit the cache first.
    if (self.objects.count == 0 || ![[UIApplication sharedApplication].delegate performSelector:@selector(isParseReachable)]) {
        [query setCachePolicy:kPFCachePolicyCacheThenNetwork];
    }

    return query;
}

另一次尝试：

- (PFQuery *)queryForTable {
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];
    [query orderByAscending:@"title"];

    // **********************************
    // PFRelation Query
    PFRelation *relation = [[PFUser currentUser] relationForKey:@"myRelation"];
    PFQuery *relationQuery = relation.query;    
    [relationQuery findObjectsInBackgroundWithBlock:^(NSArray * _Nullable objects, NSError * _Nullable error) {

        PFQuery *theQuery = [PFQuery queryWithClassName:self.parseClassName];
        [theQuery whereKey:@"title" matchesKey:@"title" inQuery:relationQuery];
        [theQuery findObjectsInBackgroundWithBlock:^(NSArray * _Nullable objects, NSError * _Nullable error) {

            NSMutableArray *arrayToShow = [NSMutableArray arrayWithArray:self.objects];

            for (PFObject *object1 in self.objects) {
                for (PFObject *object2 in objects) {
                    if ([[object1 objectForKey:@"title"] isEqualToString:[object2 objectForKey:@"title"]]) {
                        [arrayToShow removeObject:object1];
                    }
                }
            }

            self.objectsToShowArray = [NSMutableArray arrayWithArray:arrayToShow];

            [self.tableView reloadData];
        }];

    }];
    // **********************************


    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

    NSObject * object = [prefs objectForKey:@"category"];
    if(object != nil){
        //object is there
        self.categoryString = [NSString stringWithFormat:@"%@", object];

        [query whereKey:@"category" equalTo:self.categoryString];
    }

    // A pull-to-refresh should always trigger a network request.
    [query setCachePolicy:kPFCachePolicyNetworkOnly];

    // If no objects are loaded in memory, we look to the cache first to fill the table
    // and then subsequently do a query against the network.
    //
    // If there is no network connection, we will hit the cache first.
    if (self.objectsToShowArray.count == 0 || ![[UIApplication sharedApplication].delegate performSelector:@selector(isParseReachable)]) {
        [query setCachePolicy:kPFCachePolicyCacheThenNetwork];
    }

    return query;
}

同样的结果。在日志中，它正在删除正确的PFObject，但在UITableView 中，它正在删除最后一个对象。我忽略了什么？

越来越近：

我快到了。我找到了获得所需结果的正确方法，但现在我需要在查询中添加另一层。这是我的代码：

PFRelation *relation = [[PFUser currentUser] relationForKey:@"myRelation"];
PFQuery *relationQuery = relation.query;

PFRelation *adoptedRelation = [[PFUser currentUser] relationForKey:@"mySecondRelation"];
PFQuery *adoptedRelationQuery = adoptedRelation.query;

PFQuery *matchQueryOne = [PFQuery queryWithClassName:self.parseClassName];
[matchQueryOne whereKey:@"title" matchesKey:@"title" inQuery:relationQuery];

PFQuery *matchQueryTwo = [PFQuery queryWithClassName:self.parseClassName];
[matchQueryTwo whereKey:@"title" matchesKey:@"title" inQuery:adoptedRelationQuery];

 PFQuery *queryOne = [PFQuery queryWithClassName:self.parseClassName];
 [queryOne whereKey:@"title" doesNotMatchKey:@"title" inQuery:matchQueryOne];
 [queryOne whereKey:@"title" doesNotMatchKey:@"title" inQuery:matchQueryTwo];
 [queryOne orderByAscending:@"title"];

我需要运行两个关系并将结果组合起来，然后得到输出。

在这个例子中，只有我的 queryOne 中的第二种情况被命中。

Answer 1

PFQueryTableViewController 维护其要从您提供的查询中显示的项目列表。如果不取消 PFQueryTableViewController 为您提供的大部分逻辑，您就无法进行不同的查询并过滤这些结果。

更新您提供的查询 yo PFQueryTableViewController 以包含限制返回项目的子句，因此您无需在本地进行过滤。