Iphone 使用sqlite3\u column\u double检索浮点值

我对iPhone编程比较陌生，所以如果这是一个简单的问题，我很抱歉。我试图从SQLite数据库检索表FLOAT类型中的latitude/location列

我可以检索基于字符/文本的db列，但不知道如何检索浮点值。我应该使用NSString或其他东西格式化属性吗？我希望使用CLLocationDistance更下游的浮点值

// the array of locations that we will create
NSMutableArray *locations = [[[NSMutableArray alloc] init] autorelease];

const char *sql = "SELECT locations.name, \
locations.address, \
locations.city, \
locations.state, \
locations.phone, \
locations.zip, \
locations.latitude, \
locations.longitude \
FROM locations \
WHERE category = ?1";

// the sqlite statement object that will hold our result set 
sqlite3_stmt *statement;

// prepare the statement to compile the SQL query into byte-code
int sqlResult = sqlite3_prepare_v2(database, sql, -1, &statement, NULL);

// reset query before execution
sqlite3_reset(statement);

// set bind variable
sqlite3_bind_text(statement, 1, [categoryParameter UTF8String], -1, SQLITE_TRANSIENT);

if ( sqlResult== SQLITE_OK) {
    // step through the results - once for each row
    while (sqlite3_step(statement) == SQLITE_ROW) {

        // allocate a location object to add to the pharmacies array
        Location *location = [[Location alloc] init];

        // the second parameter is the column index (0 based) in
        // the result set
        char *name = (char *)sqlite3_column_text(statement, 0);
        char *address = (char *)sqlite3_column_text(statement, 1);
        char *city = (char *)sqlite3_column_text(statement, 2);
        char *state = (char *)sqlite3_column_text(statement, 3);
        char *phone = (char *)sqlite3_column_text(statement, 4);
        char *zipcode = (char *)sqlite3_column_text(statement, 5);
        float latitude = (float) sqlite3_column_double(statement, 6);
        float longitude = (float) sqlite3_column_double(statement, 7);

        // set all attributes of the location
        location.name = (name) ? [NSString stringWithUTF8String:name] : @"";
        location.address = (address) ? [NSString stringWithUTF8String:address] : @"";
        location.city = (city) ? [NSString stringWithUTF8String:city] : @"";
        location.state = (state) ? [NSString stringWithUTF8String:state] : @"";
        location.phone = (phone) ? [NSString stringWithUTF8String:phone] : @"";
        location.zipcode = (zipcode) ? [NSString stringWithUTF8String:zipcode] : @"";

        [locations addObject:location];
        [location release];
    }

    // finalize the statement to release its resources
    sqlite3_finalize(statement);

---

纬度和经度是否以度的形式存储在表中？您的Location对象是否有一个名为坐标的CLLocationCoordinate2D属性来放置坐标

如果是，只需直接设置值，因为CLLocationDegrees实际上只是一个双精度值。例如：

CLLocationCoordinate2D coords;
coords.latitude = sqlite3_column_double(statement, 6);
coords.longitude = sqlite3_column_double(statement, 7);

location.coordinates = coords;

---

纬度和经度是否以度的形式存储在表中？您的Location对象是否有一个名为坐标的CLLocationCoordinate2D属性来放置坐标

如果是，只需直接设置值，因为CLLocationDegrees实际上只是一个双精度值。例如：

CLLocationCoordinate2D coords;
coords.latitude = sqlite3_column_double(statement, 6);
coords.longitude = sqlite3_column_double(statement, 7);

location.coordinates = coords;

---

我正在存储坐标，例如40.759011和73.9844722Right，这与CLLocationDegrees相同。在Location对象中是否有存储坐标的字段？抱歉，有点混乱。在我的位置object location.h和.m中，我定义了浮动纬度；和浮动经度；好的，那么只需执行location.latitude=sqlite3。。。和location.longitude=sqlite3。。。。但是，我建议您在Location对象中将它们从float更改为CLLocationDegrees，以避免精度损失。奇怪。我以为我以前试过。看起来它正在工作。谢谢你的建议。Float四舍五入并将样本位置放置在距离其应该位置至少0.5英里的位置。我正在存储坐标，例如40.759011和73.9844722右侧，这与CLLocationDegrees相同。在Location对象中是否有存储坐标的字段？抱歉，有点混乱。在我的位置object location.h和.m中，我定义了浮动纬度；和浮动经度；好的，那么只需执行location.latitude=sqlite3。。。和location.longitude=sqlite3。。。。但是，我建议您在Location对象中将它们从float更改为CLLocationDegrees，以避免精度损失。奇怪。我以为我以前试过。看起来它正在工作。谢谢你的建议。浮子将其四舍五入，并将样本放置在距离其应放置位置至少0.5英里的位置。