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Reading a file within a factory, tokenising, vector
Templates example from a Well House Consultants training course
More on Templates [link]
Source code: flow4.cpp Module: C238
#include <iostream>
#include <fstream> #include <vector> /* Practical example of reading from a file within a factory and creating a vector of objects. Also include splitting attributes from within each line of data as the object is defined See earlier example flow2.c which uses an array rather than a vector for more detaied comments on the basic elements in this example */ using namespace std; // ------------------------------- class Train { public: Train(char *); static Train* factory(); int getcapacity(); private: static ifstream *datasource; int ncars; int spv; }; // ------------------------------- ifstream * Train::datasource = NULL; Train* Train::factory() { char trainline[256]; if (! datasource) { datasource = new ifstream("trains.txt"); } datasource->getline(trainline,256); if (datasource->eof()) { datasource->close(); return NULL; } // Next line for demonstration cout << trainline << endl; return new Train(trainline); } Train::Train(char * source) { // Source line example: Train 06:45 3 75 int starts[4]; int k=0; int param=0; while (source[k] != '\0') { if (source[k] == ' ') { source[k] = '\0'; starts[param++] = k+1; } k++; if (param > 3) break; } this->ncars = atoi(&source[starts[2]]); this->spv = atoi(&source[starts[1]]); } int Train::getcapacity() { return (int)(this->ncars * this->spv * 1.4); } // ------------------------------- int main () { // Train *service[10]; // Create me a vector to contain train services // a service is a pointer to a collection of trains (LHS) // set up a new empty collection on the heap (RHS) vector<Train *> *service = new vector<Train *>(0); int k; Train *current; while (1) { current = Train::factory(); if (! current) break; // service[traincount++] = current; // Add the new train from the factory onto the service vector service->push_back(current); } for (k=0; k<service->size(); k++) { // cout << service[k]->getcapacity() << endl; // get the service at position "k" and then get its capacity // We could use an intermediate variable - code would be longer // ... but easier to follow. cout << service->at(k)->getcapacity() << endl; } return 0; } 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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