In my program, I have a class that holds a vector of type integer. It is used to store distances. I have a function, that when called, should set values in the vector to 0's. (used for initializing). But when I go to check the size of the vector, it still says the vector is empty.
I have created multiple functions that check whether the vector is adding any elements, and it is not. I have a function, that within main, I call to see if the vector is empty, and it returns 0 (the vector has 0 elements in it).
int MLB::getDistanceSize()
{
return distances.size();
}
void MLB::setInitialDistances(int size)
{
for(int i = 0; i < size; i++)
{
this->distances.push_back(0);
}
}
class MLB
{
public:
//constructor
MLB();
~MLB();
int getDistanceSize();
void setInitialDistances(int size);
private:
vector<int> distances;
};
The input file is a csv file with each line consisting of:
stadium1,stadium2,distance
so sample input file is:
AT&T Park,Safeco Field,680
AT&T Park,Oakland–Alameda County Coliseum,50
Angel Stadium,Petco Park,110
Angel Stadium,Dodger Stadium,50
Busch Stadium,Minute Maid Park,680
Busch Stadium,Great American Ball Park,310
Busch Stadium,Target Field,465
Busch Stadium,Kauffman Stadium,235
etc...
I am using qt, and this is where I am calling the functions themselves. All information is stored into a map, and the other getters work perfectly fine. Sorry for making this a lot more confusing than the problem really is, any help is greatly appreciated.
// key and value, key is the team name, value is the MLB stadium information
struct entry
{
string key;
MLB value;
};
class Map
{
public:
//Public default constructor
Map();
//Public default destructor
~Map();
// returns entry of the map
entry atIndex(int index);
// Inserts a key and its value using linear algorithm
void insert(const string& theKey, const MLB& value);
private:
vector<entry> thisTable;
int currentSize; //Integer variable for current size
};
functions for Map:
Map::Map()
{
currentSize = 0;
}
Map::~Map()
{
}
void Map::insert(const string& theKey, const MLB& value)
{
entry thisEntry;
thisEntry.key = theKey;
thisEntry.value = value;
thisTable.push_back(thisEntry);
currentSize+=1;
}
entry Map::atIndex(int index)
{
return thisTable.at(index);
}
//mainwindow constructor
mainWindow::mainWindow()
{
//Reads in input from first csv file, all works fine all data stored and can access it
string iStadium1;
string iStadium2;
string iDistance;
string previous;
int distance;
int index1;
int index2;
bool found;
ifstream csvFile2;
csvFile2.open("inputDistance.csv");
getline(csvFile2, iStadium1, ',');
while(!csvFile2.eof())
{
index1 = 0;
found = false;
while(!found)
{
if(thisMap.atIndex(index1).value.getStadiumName() == iStadium1)
{
thisMap.atIndex(index1).value.setInitialDistances(thisMap.mapSize());
cout << "Distance Size Test 1: " << thisMap.atIndex(index1).value.getDistanceSize() << endl;
found = true;
}
else
{
index1++;
}
}
previous = iStadium1;
while(iStadium1 == previous)
{
getline(csvFile2, iStadium2, ',');
getline(csvFile2, iDistance, '\n');
distance = stoi(iDistance);
index2 = 0;
found = false;
while(!found)
{
if(thisMap.atIndex(index2).value.getStadiumName() == iStadium2)
{
found = true;
cout << "Distance Size Test 2: " << thisMap.atIndex(index1).value.getDistanceSize() << endl;
// crashes here. Index out of bounds, size is 0 for some reason
thisMap.atIndex(index1).value.setDistance(index2, distance);
}
else
{
index2++;
}
}
getline(csvFile2, iStadium1, ',');
}
}
csvFile2.close();
}
I expect the vector to hold 30 slots (assuming the desired size passed into the function is 30) of value 0, rather than having an empty vector.
The code in your question works as expected after adding constructor and destructor (doing both nothing) :
#include <iostream>
#include <vector>
using namespace std;
class MLB
{
public:
//constructor
MLB();
~MLB();
int getDistanceSize();
void setInitialDistances(int size);
private:
vector<int> distances;
};
int MLB::getDistanceSize()
{
return distances.size();
}
void MLB::setInitialDistances(int size)
{
for(int i = 0; i < size; i++)
{
this->distances.push_back(0);
}
}
MLB::MLB() {
}
MLB::~MLB() {
}
int main()
{
MLB mlb;
mlb.setInitialDistances(30);
cout << mlb.getDistanceSize() << endl;
}
pi@raspberrypi:/tmp $ g++ d.cc
pi@raspberrypi:/tmp $ ./a.out
30
the vector is not empty but contains 30 times 0
if thisMap.atIndex(index1).value.setDistance(index2, distance); does nothing this is probably because atIndex(index1) returns a copy rather than a reference, so you modify a copy and the original is unchanged
For instance :
#include <iostream>
#include <vector>
using namespace std;
class C {
public:
vector<int> getv() { return v; } // return a copy
vector<int> & getvref() { return v; } // return the ref to the vector, not a copy
int len() { return v.size(); }
private:
vector<int> v;
};
int main()
{
C c;
c.getv().push_back(0); // modify a copy of v
cout << c.len() << endl;
c.getvref().push_back(0); // modify v
cout << c.len() << endl;
}
Compilation and execution :
pi@raspberrypi:/tmp $ g++ vv.cc
pi@raspberrypi:/tmp $ ./a.out
0
1
you edited you question and this is what I supposed :
entry Map::atIndex(int index)
{
return thisTable.at(index);
}
return a copy, must be
entry & Map::atIndex(int index)
{
return thisTable.at(index);
}