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Wholesale factory - a single call to make many objects
I/O in C++ example from a Well House Consultants training course
More on I/O in C++ [link]
Source code: fullapp2.cpp Module: C235
#include <iostream>
#include <fstream> #include <vector> // Following 2 includes added Jan, 2011 #include <string.h> #include <stdlib.h> using namespace std; /* A further step towards a complete applcation, adding in a usage line and transferrring the building of the data model in a vector into a function which itself calls a factory method. This approach leads towards extensible and reuasable code, with the factory method being (in due course) stored and maintained in the files that relate to the object type rather than within the application itself. */ class Thing { public: Thing(char *); char * about(); static vector<Thing *> * wholesalefactory(char *fylenayme); private: char definition[256]; }; Thing::Thing (char * instring) { strncpy(definition,instring,255); } char * Thing::about() { return definition; } vector<Thing *> * Thing::wholesalefactory (char * sourcefile) { char myline[256]; vector<Thing *> *lynes = new vector<Thing *>(0); ifstream infile(sourcefile); if (! infile) { cerr << "Failed to open input file "<< sourcefile << endl; exit(1); } while (1) { infile.getline(myline,256); if (infile.eof()) break; // Rather than new "Thing" I could have a test to see what type of thing // I'm going to be using ... and then create various different types. // "Then it will be a proper factory" say my delegates! ;-) lynes->push_back(new Thing(myline)); } infile.close(); return lynes; } main(int argc, char **argv) { if (argc < 2) { cerr << "Usage: " << *argv << " sourcefilename" << endl; exit(2); } vector<Thing *> * shapethings = Thing::wholesalefactory(argv[1]); for (int k=shapethings->size()-1; k>=0; k--){ cout << shapethings->at(k)->about() << endl; } } /* Sample Output munchkin:c5 grahamellis$ ./fullapp2 Usage: ./fullapp2 sourcefilename munchkin:c5 grahamellis$ ./fullapp2 nosuchfile.txt Failed to open input file nosuchfile.txt munchkin:c5 grahamellis$ ./fullapp2 boring.data Rectangle 19 Circle 6 Circle 5 Square 15 Square 20 munchkin:c5 grahamellis$ */ Learn about this subject
This module and example are covered on the following public courses:
* Learning to program in C and C++ * C++ for C Programmers * C and C++ Programming * Learning to program in C and C++ * C and C++ Programming Also available on on site courses for larger groups Books covering this topic
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