如何在 iOS 中使用 PFQuery 获取 table 中的所有数据？

Question

我是 iOS 和 Parse Framework 的新手，我想从 PFQuery 的 Parse table 中获取数据，如

NSUInteger limit = 1500;
PFQuery *query = [PFQuery queryWithClassName:@"MapInfo"];
[query setLimit: limit];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
{
    if (!error) {
        NSLog(@"Successfully retrieved: %@", objects);
    } else {
        NSString *errorString = [[error userInfo] objectForKey:@"error"];
        NSLog(@"Error: %@", errorString);
    }
}];

它按我想要的方式工作，但它只给我 1000 个对象，我想在这里获取我的所有 table 数据，它包含到 2000 个对象，它会随着时间的推移增加，请帮助我这个.

为此，现在我写了这样的代码，但它只给我 1000 个对象

 NSMutableArray *allObjects = [NSMutableArray array];
NSUInteger limit = 0;
__block NSUInteger skip = 0;
PFQuery *query = [PFQuery queryWithClassName:@"MapInfo"];
[query setLimit: limit];
[query setSkip: skip];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (!error) {
        [allObjects addObjectsFromArray:objects];
        if (objects.count == limit) {

            skip += limit;
            [query setSkip: skip];
            [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
                NSLog(@"Array %@",objects);
            }];
             }

             } else {
                 NSLog(@"Error: %@ %@", error, [error userInfo]);
             }
             }];

谢谢。

Answer 1

我认为可以获取的对象数量存在查询限制。我会做的是查询对同一件事进行两次查询，但对于第二个查询，做这样的事情

[query setSkip1000];

您可以跳过第一个查询中的前 1000 个对象并获取接下来的 1000 个对象。使您的数组成为 NSMutableArray 并在每个块中执行此操作

[self.myArray addObjects:objects]; 而不是 self.myArray = objects; 这样你就覆盖了数组中的对象。

编辑

除了 2 个单独的查询，您还可以这样做

NSMutableArray *allObjectsArray = [NSMutableArray array];
//Set this to the amount of objects you want. Has to be be 1000 or less
NSUInteger limit = 0;

//Set this to the amount you want to skip (Usually 0)
NSUInteger skip = 0;
PFQuery *query = [PFQuery queryWithClassName:@"tempClass"];
[query setLimit: limit];
[query setSkip: skip];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
  if (!error) {
    // The find succeeded. Add the returned objects to allObjects
    [allObjectsArray addObjectsFromArray:objects];
    if (objects.count == limit) {
      // There could be more objects in your database. Update the skip number and perform the same query.
      skip = skip + limit;
      [query setSkip: skip];
      [query findObject...// Exactly the same way as you did before to get the rest of your objects in the database
    }

  } else {
    // Log details of the failure
    NSLog(@"Error: %@ %@", error, [error userInfo]);
  }
}];

Answer 2

https://parse.com/questions/fetch-all-data-in-a-table-using-pfquery

您可以使用 skip 和 limit 参数对 table 中的所有对象进行分页，方法是添加 limit 的值以跳过，直到查询 returns 小于 limit 的对象数量.

NSMutableArray *allObjects = [NSMutableArray array];
NSUInteger limit = 0;
__block NSUInteger skip = 0;
PFQuery *query = [PFQuery queryWithClassName:@"MapInfo"];
[query setLimit: limit];
[query setSkip: skip];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
  if (!error) {
    // The find succeeded. Add the returned objects to allObjects
    [allObjects addObjectsFromArray:objects];
    if (objects.count == limit) {
      // There might be more objects in the table. Update the skip value and execute the query again.
      skip += limit;
      [query setSkip: skip];
      [query findObjects... // Execute the query until all objects have been returned. Keep adding the results to the allObjects mutable array.

    }
  } else {
    // Log details of the failure
    NSLog(@"Error: %@ %@", error, [error userInfo]);
  }
}];

Answer 3

这是一个简单的递归解决方案，使用块从 class 中检索所有对象。

这是您最初的称呼。

[self queryAllObjectswithLimit:1000 withSkip:0 withObjects:@[] withSuccess:^(NSArray * objects) {
    //All the objects
} failure:^(NSError * error) {
    //
}];

方法在这里

- (void)queryAllObjectswithLimit:(NSUInteger )limit withSkip:(NSUInteger )skip withObjects:(NSArray *)objects withSuccess:(void (^)(NSArray *objects))success failure:(void (^)(NSError *error))failure {
//Store all the Objects through each layer of recurrsion
NSMutableArray *allObjects = [NSMutableArray arrayWithArray:objects];
PFQuery *query = [PFQuery queryWithClassName:@"Class_Name"];
query.limit = limit;
query.skip = skip;
[query findObjectsInBackgroundWithBlock:^(NSArray * _Nullable objects, NSError * _Nullable error) {
    if (!error) {
        // The find succeeded. Add the returned objects to allObjects
        [allObjects addObjectsFromArray:objects];
        if (objects.count == limit) {
            //Recursively Call this until count does not equal limit, then begin returning all the objects back up
            [self queryAllObjectswithLimit:limit withSkip:skip+limit withObjects:allObjects withSuccess:^(NSArray * objects) {
                //This will return everything
                success(objects);
            } failure:^(NSError * error) {
                failure(error);
            }];
        } else {
            success(allObjects);
        }
    } else {
        failure(error);
    }
}];

}

我已经用不到 1000 个对象、1000 个对象和超过 1000 个对象对此进行了测试，它运行良好。

请注意您抓取的对象数量，因为这会抓取所有对象，如果您处理的是大型数据集，这可能很快就会成为内存问题。

如何在 iOS 中使用 PFQuery 获取 table 中的所有数据？

How to Fetch all data in a table using PFQuery in iOS?

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