在Swift中访问C变量 [英] Access C variable in swift

问题描述

我试图访问一个状态变量在.h文件中声明，但编译器说这个变量不存在。我是否需要在桥接头文件中添加任何内容？

在我的swift文件中，我无法访问 dstate 或 cstate

编译器在 g722_coder_init（& dstate）行上使用未解析的标识符dstate' c $ c>。

头文件

  #ifdef __cplusplus 
 externC{
 #endif 
 
 extern struct g722_dstate dstate; 
 extern结构体g722_cstate cstate; 
 
 int g722_coder_init（struct g722_cstate * s）; 
 int g722_encode（short * data，unsigned char * outdata，int len，struct g722_cstate * s）; 
 int g722_decoder_init（struct g722_dstate * s）; 
 int g722_decode（unsigned char * decdata，short * pcmout，int len，struct g722_dstate * s）; 
 
 #ifdef __cplusplus 
} 
 #endif 
  

桥接标题

  #importg722_codec.h
  struct g722_dstate 是   一个不完整的类型
和Swift不能导入一个不完整类型的变量，只有变量
是指针到一个不完整类型（以及那些导入
为 OpaquePointer ）。
 
 
 
将完整的结构定义添加到导入的头文件中
是最简单的解决方案。
 
 
如果这是不可能的，那么一种解决方法是添加 
 
 
  #importg722_codec.h
 
 static struct g722_dstate * __nonnull dstatePtr =& dstate; 
  
添加到桥接头文件中，该文件定义了一个变量，其中包含不透明  dstate 变量。这被导入到Swift中作为
  var dstatePtr：OpaquePointer 
  
，然后可以使用例如作为 
 
 
  g722_coder_init（dstatePtr）
  
 
I'm trying to access a state variable declare in .h file but the compiler said the variable doesn't exist. Do I need to add anything in my bridging header file ? 

In my swift file I can't access dstate or cstate

The compiler says "Use of unresolved identifier 'dstate'" on the line g722_coder_init(&dstate).



Header file
#ifdef __cplusplus
extern "C" {
#endif

extern struct g722_dstate dstate;
extern struct g722_cstate cstate;

int g722_coder_init (  struct g722_cstate *s  );
int g722_encode(short *data, unsigned char *outdata,int len, struct g722_cstate *s  );
int g722_decoder_init (  struct g722_dstate *s);
int  g722_decode(unsigned char *decdata, short *pcmout, int len,  struct g722_dstate *s );

#ifdef __cplusplus
}
#endif
Bridging Header
#import "g722_codec.h"

解决方案
The problem is that struct g722_dstate is an "incomplete type",
and Swift cannot import variables of an incomplete type, only variables
which are  pointers to an incomplete type (and those are imported
as OpaquePointer).

Adding the complete struct definition to the imported header file would
be the easiest solution.

If that is not possible then one workaround would be to add
#import "g722_codec.h"

static struct g722_dstate * __nonnull dstatePtr = &dstate;
to the bridging header file, which defines a variable containing the
address of the "opaque" dstate variable. This is imported to Swift as
var dstatePtr: OpaquePointer
and can then be used e.g. as
g722_coder_init(dstatePtr)


                        
这篇关于在Swift中访问C变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！