如何将SQlite扩展源文件链接到iPhone的Xcode？ [英] How to link a SQlite Extension Source File into Xcode for iPhone?

问题描述

我在iPhone Xcode项目中为Sqlite使用静态链接库。我现在正试图在这个项目中包含一个.c扩展名到Sqlite。但是，我在构建中使用Sqlite时遇到问题SEE扩展。

I use a statically linked library for Sqlite in an iPhone Xcode project. I am now trying to include a .C extension to Sqlite in this project. However, I am having trouble making the Sqlite in the build SEE the extension.

静态链接的Sqlite库工作正常。此.C扩展也适用于我的桌面，并在Xcode中作为静态链接库构建良好。但是，调用它时定义的自定义函数会丢失。

The statically linked Sqlite library works fine. Also the .C extension works on my desktop, and builds fine as a statically linked library in Xcode. However, the custom functions it defines are missing when called.

例如，我加载了扩展名，没有错误。

For example, I load the extension as so with no errors.

SELECT load_extension('extension_name.so');

但是当我尝试调用扩展中定义的函数时，我收到此消息

But when I try to call a function defined in the extension, I get this message

DB Error: 1 "no such function: custom_function"

有没有人知道将Sqlite扩展链接到Xcode项目？

Does anyone know much about linking a Sqlite extension into an Xcode project?

推荐答案

As @jbworld说你不能在iPhone上加载动态库，所以这个链接应该在编译时静态创建。在阅读spatialite的代码（这是一个SQLite扩展）时，我发现了这种调用：

As said by @jbworld you cannot load dynamic libraries on the iPhone, so this link should be made statically, at compilation time. While reading at the code of spatialite (that's an SQLite extension), I found that kind of invocation:

void spatialite_init (int verbose) {
/* used when SQLite initializes SpatiaLite via statically linked lib */
    sqlite3_auto_extension ((void (*)(void)) init_static_spatialite);
}

init_static_spatialite 代码：

static void init_static_spatialite (sqlite3 * db, char **pzErrMsg,
            const sqlite3_api_routines * pApi)
{
    SQLITE_EXTENSION_INIT2 (pApi);
/* setting the POSIX locale for numeric */
    setlocale (LC_NUMERIC, "POSIX");
    *pzErrMsg = NULL;
    sqlite3_create_function (db, "spatialite_version", 0, SQLITE_ANY, 0,
                             fnct_spatialite_version, 0, 0);
    sqlite3_create_function (db, "proj4_version", 0, SQLITE_ANY, 0,
                             fnct_proj4_version, 0, 0);
    sqlite3_create_function (db, "geos_version", 0, SQLITE_ANY, 0,
                             fnct_geos_version, 0, 0);
    sqlite3_create_function (db, "GeometryConstraints", 3, SQLITE_ANY, 0,
                             fnct_GeometryConstraints, 0, 0);
    sqlite3_create_function (db, "CheckSpatialMetaData", 0, SQLITE_ANY, 0,
                             fnct_CheckSpatialMetaData, 0, 0);
...

所以看起来如果 sqlite_auto_extension 使您可以静态链接扩展名。 文档似乎确认：

So it looks like if the sqlite_auto_extension enables you to statically link an extension. The documentation seems to confirm that:

可以在程序启动时调用此API，以便注册一个或多个可用于所有新数据库连接的静态链接扩展。

"This API can be invoked at program startup in order to register one or more statically linked extensions that will be available to all new database connections."

然后，在运行时，对于spatialite，我只需要调用 spatialite_init（0）来获得扩展名

Then, at runtime, for spatialite, I just have to invoke the spatialite_init(0) to get the extension up and running.

希望这有帮助。

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