将mapView.userLocation.location.coordinate.longitude保存到sqlite数据库中 [英] Saving mapView.userLocation.location.coordinate.longitude into sqlite database

问题描述

我想将从mapView.userLocation.location.coordinate.longitude返回的值插入到我的sqlite3数据库中.我不确定它的类型.我不能这样:

I want to insert the value returning from mapView.userLocation.location.coordinate.longitude into my sqlite3 database. I am not sure of its type. I cannot do it this way:

sqlite3_bind_text(stmt, 1, [mapView.userLocation.location.coordinate.longitude floatValue], -1, nil);

我认为这会导致无法转换为指针类型" 错误，因为经度不是浮动的.

It gives "Cannot convert to a pointer type" error because longitude is not float, I guess.

数据库表中字段的类型为FLOAT.如何将经度值转换为浮点值?

The type of field is FLOAT in the database table. How can I convert the value of longitude to float from whatever it is?

非常感谢.

推荐答案

MKUserLocation的文档显示location属性的类型为CLLocation. CLLocation的文档显示，ordinate属性的类型为CLLocationCoordinate2D.

The documentation for MKUserLocation shows that the location property is of type CLLocation. The docs for CLLocation show that the coordinate property is of type CLLocationCoordinate2D.

核心位置数据类型参考显示CLLocationCoordinate2D是一个包含纬度和经度的结构，每个结构的类型均为CLLocationDegrees.

The Core Location Data Types Reference shows that CLLocationCoordinate2D is a struct containing latitude and longitude each of which is of type CLLocationDegrees.

在同一页面上，CLLocationDegrees被显示为double的另一个名称.因此，纬度和经度是double类型的.

On the same page, CLLocationDegrees is shown to be just another name for double. So latitude and longitude are of type double.

因此，不要使用sqlite3_bind_text，而要使用sqlite3_bind_double:

So instead of using sqlite3_bind_text, use sqlite3_bind_double:

sqlite3_bind_double(stmt, 1, mapView.userLocation.location.coordinate.longitude);

并加载该值，您将使用类似以下内容的

and to load the value, you would use something like:

double longitude = sqlite3_column_double(stmt, column_index_here);

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