Parse TableView 中的位置查询

问题描述

我有一个 PFQueryTableView，它应该收集 10 个最近的商店位置并按距离顺序显示它们.我像这样查询 tableview:

I have a PFQueryTableView which is supposed to gather the 10 closest store locations and display them in order of proximity. I query the tableview like so:

    - (PFQuery *)queryForTable {
    PFQuery *query = [PFQuery queryWithClassName:@"TopToday"];
    query.limit = 7;
    CLLocation *currentLocation = locationManager.location;
    PFGeoPoint *userLocation =
    [PFGeoPoint geoPointWithLatitude:currentLocation.coordinate.latitude
                           longitude:currentLocation.coordinate.longitude];

    return query;
}

上面的代码工作正常，只是不按特定顺序收集了 7 个随机位置.但是，当我添加这一行时:

The above code works fine, just gathers 7 random locations in no particular order. However, when I add this line:

[query whereKey:@"location" nearGeoPoint:userLocation withinMiles:50];

它只返回一个空白的默认tableview.有没有人有任何想法我为什么查询不适用于位置线?

It just returns a blank default tableview. Does anyone have any thoughts I why the query does not work with the location line?

推荐答案

我的猜测是查询正在您的位置管理器返回有效位置之前运行.

My guess is that the query is being run before your location manager returns a valid location.

我会为当前地理点创建一个新属性；

I'd create a new property for the current geopoint;

@property (nonatomic, strong) PFGeoPoint *currentGeoPoint;

然后覆盖 loadObjects 以确保在查询运行之前地理点确实存在.

Then override loadObjects to make sure the geo point actually exists before the query runs.

- (void)loadObjects
{
    if (!self.currentGeoPoint)
    {
        [PFGeoPoint geoPointForCurrentLocationInBackground:^(PFGeoPoint *geo, NSError *error)
         {
             self.currentGeoPoint = geo;
             [super loadObjects];
         }];
    }
    else
    {
        [super loadObjects];
    }
}

最后在查询中引用 currentGepoint.

And finally reference the currentGepoint in your query.

- (PFQuery *)queryForTable
{
    PFQuery *query = [PFQuery queryWithClassName:@"TopToday"];
    query.limit = 7;
    [query whereKey:@"location" nearGeoPoint:self.currentGeoPoint withinMiles:50];
    return query;
}

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