static const member initialization from file - c++

Question

How do you initialize a static const member with a value that is stored in a file? For example:
Class Foo
{
private:
static const String DataFromFile;
void InitData (void);
};
I know for a short value, I can initialize with:
const String DataFromFile = "Some Value";
But what if the value is really a "big" value and encrypted and stored in a disk file? I need to decrypt it before putting it into DataFromFile.
Is there a way to do it or can I just forget it and treat it as a regular variable? That is, instead of:
static const String DataFromFile;
can I just declare it as:
String DataFromFile;
and initialize it with a function?

Answer 1

How do you initialize a static const member with a value that is
stored in a file? For example:
Like this:
//X.h
#include <string>
class X
{
//...
static const std::string cFILE_TEXT_;
static const bool cINIT_ERROR_;
};
//X.cpp
//...#include etc...
#include <fstream>
#include <stdexcept>
namespace {
std::string getTextFromFile( const std::string& fileNamePath )
{
std::string fileContents;
std::ifstream myFile( fileNamePath.c_str() );
if( !(myFile >> fileContents) );
{
return std::string();
}
return fileContents;
}
}
const std::string X::cFILE_TEXT_( getTextFromFile( "MyPath/MyFile.txt" ) );
const bool X::cINIT_ERROR_( cFILE_TEXT_.empty() );
X::X()
{
if( cINIT_ERROR_ )
{
throw std::runtime_error( "xxx" );
}
}