interface - C++ multiple data sources within class -


i wonder how 1 go adding different data sources existing code. example, let's have piece of code:

//datafromfile.cpp  #include "data.h"  class datafromfile { public:     datafromfile() { filename = ""; }     ~datafromfile() { delete data; }     void loadvalue(const char *filename) { //getting data file }     void printdata() { data->printdata(); } private:     string filename;     data *data; };   //source.cpp  #include <iostream> #include "datafromparameter.h"  int main(int argc, char **argv) {     datafromfile olddata;     olddata.loadvalue("example.txt");     olddata.printdata();     return 0; }

and need create class datafromdatabase or datafromparameter without changing way datafromfile works (this code used throughout various programs , going through code out of question). creating interface seemed way go, came solution:

//idata.h  #include "data.h"  class idata { public:     idata() { data = null; }     virtual ~idata() = 0 { delete data; }     void printdata() { if (data != null) data->printdata(); } protected:     data *data; }  //datafromparameter.h  #include "idata.h"  class datafromparameter : public idata { public:     datafromparameter(const int value) { this->data = new data(value); }     ~datafromparameter() {} };   //datafromfile.h  #include "idata.h"  class datafromfile : public idata { public:     datafromfile() { filename = ""; }     datafromfile(const char *filename) { loadvalue(filename); }     ~datafromfile() {}     void loadvalue(const char *filename) { //getting data file } private:     string filename; }

as can see idata , datafromparameter new classes , added methods datafromfile. creating new objects , calling methods:

//source.cpp  #include <iostream> #include "datafromparameter.h"  int main(int argc, char **argv) {     //source: file (the old way)     datafromfile olddata;     olddata.loadvalue("example.txt");     olddata.printdata();      //source: file (the new way)     idata *newdata1 = new datafromfile("example.txt");     newdata1->printdata();     delete newdata1;      //source: parameter     idata *newdata2 = new datafromparameter(atoi(argv[1]));     newdata2->printdata();     delete newdata2;     return 0; }

it works, nevertheless i'm not happy it; datafromfile class code looks messy - know why looks way sure else pretty confused going on in there.

my question is: there better way go here? sloppiness necessary (given circumstances) or missing obvious solution problem?


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