Define static method in source-file with declaration in header-file in C

Question

I am having a little trouble working with static methods in C    Example  h   class IC Utility   public      IC Utility         IC Utility         std  string CP PStringToString  const unsigned char  outString        void CP StringToPString  std  string amp  inString  unsigned char  outString  short inMaxLength        static void CP StringToPString  std  string amp  inString  unsigned char  outString       void CP StringToPString  FxString amp  inString  FxUChar  outString         Example  cpp   static void IC Utility  CP StringToPString std  string amp  inString  unsigned char  outString        short       length   inString length        if  outString    NULL                 if  length  gt   1               CPLAT  CP Utility  CP CopyMemory  inString c str     amp outString  1    length                 outString  0     length            I wanted to make a call like   IC Utility  CP StringToPString directoryNameString  directoryName      But I get an error   error  cannot declare member function  static void IC Utility  CP StringToPString std  string amp   unsigned char    to have static linkage   I dont understand why I cannot do this  Can anyone help me understand why and how to achieve what I want

User · Answer

Static member functions must refer to static variables of that class. So in your case,

static void CP_StringToPString( std::string& inString, unsigned char *outString);

Since your member function CP_StringToPstring is static, the parameters in that function, inString and outString should be declared as static too.

The static member functions does not refer to the object that it is working on but the variables your declared refers to its current object so it return error.

You could either remove the static from the member function or add static while declaring the parameters you used for the member function as static too.

User · Answer

Remove static keyword in method definition  Keep it just in your class definition   static keyword placed in  cpp file means that a certain function has a static linkage  ie  it is accessible only from other functions in the same file

User · Answer

Keywords static and virtual should not be repeated in the definition  They should only be used in the class declaration

User · Answer

Probably the best course of action is  quot do it as std lib does it quot   That is  All inline  all in headers     in the header namespase my namespace       class my standard named class final   public           static void standard declared defined method                     even the comment is standard                         namespase my namespace    As simple as that

User · Answer

You don t need to have static in function definition

[c++] Define static method in source-file with declaration in header-file in C++

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