Why doesn't the spare vector copy into the existing vector?

[AL88]

Why doesn't the spare vector copy into the existing vector on line 234?

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<fstream>
#include<iomanip>
#include<stdlib.h>

using namespace std;

struct addressCard
{
string name;
string street;
string town;
string county;
string postCode;
string country;
int telephoneNumber;
};


// write to an output stream, object into a stream
ostream& operator<< ( ostream& stm, const addressCard& a )
    // write one string per line, end with a blank line
{
    return stm << a.name << '\n' << a.street << '\n' << a.town << '\n' 
<< a.county << '\n' << a.postCode << '\n' << a.country << "\n\n" ;
}

// read from an input stream
istream& operator>> ( istream& stm, addressCard& a )
{
    // read one line per string, ignore blank lines at the beginning

    // read the first line, after skipping over blank lines
    while( getline( stm, a.name ) && a.name.empty() ) ;

    // read the remaining lines
    if( getline( stm, a.street ) && getline( stm, a.town ) 
&& getline( stm, a.county ) && getline( stm, a.postCode ) 
&& getline( stm, a.country ) ) ; // do nothing more
    else a = {} ; // clear all fields in a

    return stm ;
}

bool genericSort(const addressCard &obj1, const addressCard &obj2) {
	if (obj1.name == obj2.name)
		if (obj1.street == obj2.street)
			if (obj1.town == obj2.town)
				if (obj1.county == obj2.county)
					if (obj1.postCode == obj2.postCode)
						return obj1.country < obj2.country;
					else
						return obj1.postCode < obj2.postCode; //same as the 
//correspondent if condition, replace == with <
				else
					return obj1.county < obj2.county;
			else
				return obj1.town < obj2.town;
		else
			return obj1.street < obj2.street;
	else
		return obj1.name < obj2.name;

}

const unsigned numberOfPeople = 3;

int main()
{
vector<addressCard> people(numberOfPeople);

for (vector<addressCard>::size_type i = 0; i!=numberOfPeople; ++i)
{
cout <<"Person# " <<i+1<< " name: " << endl;
getline(cin,people[i].name);

cout <<"Person# " <<i+1<< " street: " << endl;
getline(cin,people[i].street);

cout <<"Person# " <<i+1<< " town: " << endl;
getline(cin,people[i].town);

cout <<"Person# " <<i+1<< " county: " << endl;
getline(cin,people[i].county);

cout <<"Person# " <<i+1<< " postCode: " << endl;
getline(cin,people[i].postCode);

cout <<"Person# " <<i+1<< " country: " << endl;
getline(cin,people[i].country);

}

cout <<"\n\n";


cout <<"Sorting....\n";

sort(people.begin(), people.end(), genericSort);

cout <<"Printing results....\n";

for (addressCard &n : people)
{
cout << n.name << endl;
cout << n.street << endl;
cout << n.town << endl;
cout << n.county << endl;
cout << n.postCode << endl;
cout << n.country << endl;

cout <<"\n\n";
}

cout <<"Printing raw vector....\n";

for (vector<addressCard>::size_type i = 0; i!=numberOfPeople; ++i)
{
cout <<people[i].name << endl;

cout <<people[i].street << endl;

cout << people[i].town << endl;

cout <<people[i].county << endl;

cout << people[i].postCode << endl;

cout <<people[i].country << endl;

cout <<"\n\n";

}

cout <<"Writing to file....\n";

const string file_name = "data.txt" ;

        ofstream ofile(file_name) ;
        for( const addressCard& a : people ) ofile << a ; //vector 
//favourites of class type addressCard, object a iterates vector
// and writes it to text file
ofile.close();

cout<<"Writing text file to screen...\n\n";

    string x;
    ifstream inFile;

    inFile.open("data.txt");
    if (!inFile) {
        cout << "Unable to open file";
        return(1); // terminate with error
    }

    while (getline(inFile,x)) {
cout << x << endl ;
}

    inFile.close();

cout <<"Loading text file into existing vector....\n";

        ifstream ifile(file_name) ; //ifstream reads text file
        addressCard a ; //new object
        people.clear(); //clears existing vector
        cout << people.size() << " size of array after clear\n\n" ;        
        while( ifile >> a ) people.push_back(a) ; //object a reads from text
// file, fills existing vector people
        cout << people.size() << " items were read\n\n" ;

        for( const auto& a : people ) cout << a ;


cout <<"Adding an element to the vector....\n";

addressCard addedObj;
addedObj = {"Jonathan Zebes","26 Grovsenor St","Chester","Cheshire",
"CH8 9PO","UK"};
people.push_back(addedObj);

cout << "Printing out vector....\n";

for (addressCard &n : people)
{
cout << n.name << endl;
cout << n.street << endl;
cout << n.town << endl;
cout << n.county << endl;
cout << n.postCode << endl;
cout << n.country << endl;

cout <<"\n\n";
}


cout << "Adding several elements to the existing vector.\n";
cout << "How many elements would you like to add?\n";

int numberOfExtraPeople;

cin>>numberOfExtraPeople;

cin.ignore();

vector<addressCard> spareVector(numberOfExtraPeople); 

for (vector<addressCard>::size_type i = 0; i!=numberOfExtraPeople; ++i)
{
cout <<"Person# " <<i+1<< " name: " << endl;
getline(cin,spareVector[i].name);

cout <<"Person# " <<i+1<< " street: " << endl;
getline(cin,spareVector[i].street);

cout <<"Person# " <<i+1<< " town: " << endl;
getline(cin,spareVector[i].town);

cout <<"Person# " <<i+1<< " county: " << endl;
getline(cin,spareVector[i].county);

cout <<"Person# " <<i+1<< " postCode: " << endl;
getline(cin,spareVector[i].postCode);

cout <<"Person# " <<i+1<< " country: " << endl;
getline(cin,spareVector[i].country);

}

cout <<"Copying spare vector to existing vector...\n";  
    for (int i=0; i<people.size(); i++) 
        spareVector.push_back(people[i]); 
  
cout <<"Outputting existing vector....\n";

for (addressCard &n : people)
{
cout << n.name << endl;
cout << n.street << endl;
cout << n.town << endl;
cout << n.county << endl;
cout << n.postCode << endl;
cout << n.country << endl;

cout <<"\n\n";
}

return 0;

}

[salem c]

> cout <<"Copying spare vector to existing vector...\n";
Because you're pushing INTO spareVector, not into people.

Oh, and 250 lines of badly indented code is no fun to read.

No to mention, a main() well over 100 lines long.

Create some functions to separate the work-flow into easily recognisable and manageable steps.

[ne555]

cout <<"Copying spare vector to existing vector...\n";  
    for (int i=0; i<people.size(); i++) 
        spareVector.push_back(people[i]); 

that reads: traverse 'people' and put its elements onto `spareVector'
you've got it backwards
people.insert(people.end(), spareVector.begin(), spareVector.end());

[AL88]

Why isn't this having any effect even though it compiles

int eraseElement()
{
int position;
cout <<"What position would you like to erase?\n";
cin>>position;
cout <<"Erasing position" <<position<< "\n";
people.erase (people.begin()+(position+1));
}

please help me know how to delete specified element. Thanks.

[E0p9LyTq]

It doesn't work because you are supplying the wrong data type for the method to work.

erase requires a vector iterator, or a range defined by iterators, to work. position is an int.

https://en.cppreference.com/w/cpp/container/vector/erase

Stop using the wrong data type and erase will work for you.

Misread the erase parameter, my bad. Mea culpa.

[keskiverto]

This is valid:
people.erase( people.begin() + position + 1 );
because the people.begin() + position is an iterator + integer that returns an iterator.

If that were "supplying the wrong data type for the method", then it would be a syntax error at compile-time.


However,

int eraseElement()
{
  int position;
  cin>>position;
  people.erase( people.begin()+(position+1) );
}

Should get a warning, because it does not return any integer despite promising to do so.

Furthermore:
* The input could fail. (What integer value is "Dolly"?)
* There is no safety check that -2 < position < people.size()-1
* The logic of showing "Erasing position 41" when you actually erase position 42 is atrocious.


We don't know where you do use that function nor how you test it.

[E0p9LyTq]

I misread the parameter, I screwed up. I focused on the position+1.

Which as you point out is still wrong. Thanks for giving me a Gibbs slap, it was needed.