Static methods in C++ | 易学教程

问题

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

};

Example .cpp:

static void IC_Utility::CP_StringToPString(std::string& inString, unsigned char *outString)
{
    short       length = inString.length();

   if( outString != NULL )
    {
        if( length >= 1 )
            CPLAT::CP_Utility::CP_CopyMemory( inString.c_str(), &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&, 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?

回答1:

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.

回答2:

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

回答3:

You don't need to have static in function definition

回答4:

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.

来源：https://stackoverflow.com/questions/5980520/static-methods-in-c

标签

c++

static-linking