设置NSManagedObject上的double属性的值 [英] Setting the value of a double attribute on NSManagedObject

问题描述

我试图在我的应用程序上实现地图功能。然而，我想要的纬度和经度从存储在核心数据中的对象传递到地图。但是，当我启动我的应用程序时，我有问题设置对象的初始值。我尝试了两种不同的方式到目前为止，每个和错误我收到的是发送双参数的不兼容的类型'id'。任何帮助将非常感激。

I am trying to implement a maps feature on my application. However to I would like the latitude and longitude be passed into the map from an object that is stored in core data. However I am having problem setting the initial value on the object when I start my application. I have tried 2 different ways so far and each and error I receive is "Sending 'double to a parameter of incompatible type 'id'. Any help would be very appreciated.

NSManagedObject *room = [NSEntityDescription insertNewObjectForEntityForName:@"Room" inManagedObjectContext:context];

    double myLatitude = -1.228087;
    double myLongitude = 52.764397;

    [room setValue:@"H001" forKey:@"code"];
    [room setValue:@"This is a description" forKey:@"roomDescription"];
    [room setValue:myLatitude forKey:@"longitude"];
    [room setValue:myLatitude forKey:@"latitude"];

推荐答案

NSManagedObject 属性需要是对象，但 double 是一个原始的C类型。解决方案是在 NSNumber 中封装双精度：

NSManagedObject attributes need to be objects, but double is a primitive C type. The solution is to wrap the doubles in an NSNumber:

[room setValue:[NSNumber numberWithDouble:myLongitude] forKey:@"longitude"];
[room setValue:[NSNumber numberWithDouble:myLatitude] forKey:@"latitude"];

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