浮点数的核心数据谓词过滤

问题描述：

基本上，我有一个MKMapView的位置数据库，当每个注释的详细信息显示按钮被点击时，它会显示更多的位置信息，例如他们的网站和电话号码。浮点数的核心数据谓词过滤

问题是，在我的数据库中，一些坐标只有4或5个小数点而不是6个，所以当点击按钮时，应用程序会崩溃。要停止此操作，我在UIAlertView中添加了“我们无法找到更多信息” 有什么方法可以更好地使用我的谓词吗？

NSString *lat = [NSString stringWithFormat:@"%.6f", view.annotation.coordinate.latitude]; 
NSString *lon = [NSString stringWithFormat:@"%.6f", view.annotation.coordinate.longitude]; 
NSFetchRequest *request = [[NSFetchRequest alloc] init]; 
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Stores" inManagedObjectContext:_managedObjectContext]; 
[request setEntity:entity]; 
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"Latitude == %@ && Longitude == %@", lat, lon]; 
[request setPredicate:predicate]; 

NSError *error = nil; 
NSArray *stores = [_managedObjectContext executeFetchRequest:request error:&error]; 
[request release]; 
if (![stores count]) { 
    UIAlertView *alert = [[[UIAlertView alloc]initWithTitle:@"Error" message:@"Sorry, we are unable to locate more information for this location." delegate:nil cancelButtonTitle:@"Okay" otherButtonTitles: nil]autorelease]; 
    [alert show]; 
} else { 



    Stores *currentStore = [stores objectAtIndex:0]; 
    NSLog(@"current store %@", currentStore); 

    AddressAnnotation *annotation = view.annotation; 

    MoreInfoTable *moreInfoView = [[MoreInfoTable alloc] initWithStyle:UITableViewStyleGrouped]; 
    moreInfoView.currentStore = currentStore; 
    moreInfoView.managedObjectContext = self.managedObjectContext; 
    moreInfoView.title = annotation.title ; 
    moreInfoView.getWebsite =[NSURL URLWithString:annotation.website]; 
    moreInfoView.getDirections = [NSURL URLWithString:[NSString stringWithFormat:@"http://maps.google.com/maps?saddr=%f,%f&daddr=%f,%f", mapView.userLocation.coordinate.latitude, mapView.userLocation.coordinate.longitude, annotation.coordinate.latitude, annotation.coordinate.longitude]]; 
    moreInfoView.footer = [NSString stringWithFormat:@"%.1f miles away", annotation.distanceFromLocation]; 
    moreInfoView.address = annotation.address; 
    moreInfoView.getPhoneNumber = [NSMutableString stringWithString:annotation.phoneNumber]; 
    moreInfoView.lat = view.annotation.coordinate.latitude; 
    moreInfoView.lon = view.annotation.coordinate.longitude; 

    [self.navigationController pushViewController:moreInfoView animated:YES]; 
    [moreInfoView release]; 

} 

}

答

我假设你正试图让所有的存储实体有经济或经济。你应该检查纬度或经度！=零，而不是比较你的6位十进制字符串。

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"Latitude != nil && Longitude != nil"]; 
[request setPredicate:predicate];

浮点数的核心数据谓词过滤

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