在解析查询中添加 mapview 注释会随机返回 null
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【中文标题】在解析查询中添加 mapview 注释会随机返回 null【英文标题】：Adding mapview annotations within parse query returns null randomly 【发布时间】：2014-05-10 19:50:13 【问题描述】：我正在使用 Parse 数据库（异步）创建一个 ios 应用程序来存储将在填充地图视图时使用的信息。很长一段时间以来，我一直试图找出问题所在，并且在没有任何运气的情况下进行了大量研究。不过，我已经找到了问题的根源。
在我的代码中，我正在查询解析数据库，希望得到我想要的信息，然后将信息存储在自定义 pointAnnotation 类中，该类是 MkPointAnnotation 类型。每个项目都存储在一个pointAnnotations数组中，一旦数据库中的所有项目都存储在数组中，注释就会添加到MyMapView。 --我已经尝试在创建注释时添加它们，这不会改变任何东西。
我遇到的问题是，随机查询将在 for(PFObject *vendor in Vendors) 下迭代并遇到错误，调用 NSLog(@"%@", error.debugDescription);在输出日志中显示 (null)。每次我运行应用程序时，返回 null 的对象数量似乎都会发生变化，有时它会按预期工作。添加 do while(pointArray.count
这是 Parse 效率低下还是有更好的方法来实现预期结果？
PFQuery *query = [PFQuery queryWithClassName:@"Vendors"];
[query orderByDescending:@"updatedAt"];
[query findObjectsInBackgroundWithBlock:^(NSArray *vendors, NSError *error)
NSMutableArray *pointArray = [[NSMutableArray alloc] init];
if (!error)
// The find succeeded.
// Do something with the found objects
do
pointArray = [[NSMutableArray alloc] init];
for (PFObject *vendor in vendors)
NSDate *lastUpdated = vendor.updatedAt;
NSDate *today = [NSDate date];
NSDate *newDate = [lastUpdated dateByAddingTimeInterval:86400];
if (today <= newDate)
PFGeoPoint *point = vendor[@"Location"];
NSString *vendor_ID = vendor[@"Vendor_ID"];
NSMutableArray *FruitList = vendor[@"Fruits"];
NSMutableArray *VeggieList = vendor[@"Veggies"];
NSMutableArray *addressArray = vendor[@"Address"];
NSString *startHr = vendor[@"Start_Time"];
NSString *endHr = vendor[@"End_Time"];
Boolean more = false;
NSString *moreString = vendor[@"And_More"];
if ([moreString isEqual: @"true"])
more = true;
CLLocationCoordinate2D location;
location.latitude = point.latitude;
location.longitude = point.longitude;
pointAnnotation *newAnnotation = [[pointAnnotation alloc] init];
if ([[[NSUserDefaults standardUserDefaults] objectForKey:@"language"] isEqual:@"ENGLISH"])
FindCartsLabel.text = @"Find Carts within:";
MilesTextField.text = @"Show All";
milesArray=[[NSArray alloc]initWithObjects:@"Show All", @"1 Mile", @"5 Miles", @"10 Miles", @"20 Miles", nil];
AddressBar.placeholder = ENGLISH_Address;
newAnnotation.title = @"Good. To. Go. Vendor";
newAnnotation.fruits = FruitList;
newAnnotation.veggies = VeggieList;
else if ([[[NSUserDefaults standardUserDefaults] objectForKey:@"language"] isEqual:@"SPANISH"])
FindCartsLabel.text = @"Encuentra Carros Dentro:";
newAnnotation.title = @"Good. To. Go. Vendedor";
AddressBar.placeholder = SPANISH_Address;
NSMutableArray *spanishFruitList = [[NSMutableArray alloc]init];
for (NSString *current in FruitList)
MilesTextField.text = @"Mostrar Todo";
milesArray=[[NSArray alloc]initWithObjects:@"Mostrar Todo", @"1 Milla", @"5 Millas", @"10 Millas", @"20 Millas", nil];
if ([current isEqual:@"Apples"])
[spanishFruitList addObject:SPANISH_Apples];
if ([current isEqual:@"Bananas"])
[spanishFruitList addObject:SPANISH_Bananas];
if ([current isEqual:@"Citrus"])
[spanishFruitList addObject:SPANISH_Citrus];
if ([current isEqual:@"Mangos"])
[spanishFruitList addObject:SPANISH_Mangos];
if ([current isEqual:@"Strawberries"])
[spanishFruitList addObject:SPANISH_Strawberries];
if ([current isEqual:@"And More"])
[spanishFruitList addObject:SPANISH_More];
NSMutableArray *spanishVeggieList = [[NSMutableArray alloc]init];
for (NSString *current in VeggieList)
if ([current isEqual:@"Avocados"])
[spanishVeggieList addObject:SPANISH_Avocados];
if ([current isEqual:@"Broccoli"])
[spanishVeggieList addObject:SPANISH_Broccoli];
if ([current isEqual:@"Carrots"])
[spanishVeggieList addObject:SPANISH_Carrots];
if ([current isEqual:@"Squash"])
[spanishVeggieList addObject:SPANISH_Squash];
if ([current isEqual:@"Onions"])
[spanishVeggieList addObject:SPANISH_Onions];
if ([current isEqual:@"Tomatoes"])
[spanishVeggieList addObject:SPANISH_Tomatoes];
if ([current isEqual:@"And More"])
[spanishVeggieList addObject:SPANISH_More];
newAnnotation.fruits = spanishFruitList;
newAnnotation.veggies = spanishVeggieList;
newAnnotation.coordinate = location;
newAnnotation.vendorID = vendor_ID;
newAnnotation.startHour = startHr;
newAnnotation.endHour = endHr;
newAnnotation.loc = point;
newAnnotation.isCustomAddress = false;
//newAnnotation.subtitle = address;
__block NSString *address = [NSString stringWithFormat:@"%@ %@, %@, %@, %@",
addressArray[0], addressArray[1],
addressArray[2], addressArray[3],
addressArray[4]];
__block NSString *currAddress = [NSString stringWithFormat:@"%@ %@\n"
"%@, %@, %@\n"
"%@\n",
addressArray[0], addressArray[1],
addressArray[2], addressArray[3],
addressArray[4], addressArray[5]];
newAnnotation.subtitle = address;
newAnnotation.addressFormatted = currAddress;
static NSString *identifier = @"MyLocation";
MKPinAnnotationView *currentView = [[MKPinAnnotationView alloc] initWithAnnotation:newAnnotation reuseIdentifier:identifier];
[pointArray addObject:currentView];
else
//[self viewDidLoad];
NSLog(@"%@", error.debugDescription);
// ];
while (pointArray.count < query.countObjects);
if (pointArray.count == query.countObjects)
for (MKPinAnnotationView *currentPoint in pointArray)
[self.MyMapView addAnnotation:currentPoint.annotation];
];
提前感谢您的帮助。我真的不明白为什么这段代码只在一次迭代后就无法完成。
【问题讨论】：
NSLog(@"%@", error.debugDescription); 看起来位置不对。它位于与if (today <= newDate) 关联的else 块中，if (today <= newDate) 位于 inside 代码块中，仅当error 为 null 时才会执行，这就是它在日志中显示 null 的原因（当真正的意思是“今天 > 新日期”）。
error 的 NSLog 应该更远——可能就在 if (pointArray.count == query.countObjects) 之前。
不相关 但是：您应该只在 viewForAnnotation 委托方法中创建 MKPinAnnotationView 对象。在这段代码中，您应该将pointAnnotation 对象本身添加到pointArray，然后最后您可以执行[self.MyMapView addAnnotations:pointArray];（无需循环）。
哇，我不敢相信我错过了。非常感谢。
【参考方案1】：
NSLog(@"%@", error.debugDescription);看起来它不在正确的位置。它位于与 if (today 新日期”）。 ——安娜
【讨论】：
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