I create an object and try to pass that object through multiple function by reference
#include<iostream>
#include <string>
#include "DBMS.h"
using namespace std;
void Home(DBMS &);
int main()
{
DBMS dbms();
Home(dbms); // this is where the error is
return 0;
}
void Home(DBMS &dbms)
{
string dbName;
dbms.addDatabase(dbName);
}
and this is DBMS.h
#pragma once
#include <iostream>
#include <string>
#include <vector>
#include "Database.h"
using namespace std;
class DBMS
{
public:
DBMS();
void addDatabase(string);
Database& getDatabase(string);
Database& getDatabaseByIndex(int);
int getDatabaseIndex(string);
void removeDatabase(string);
int size();
~DBMS();
private:
vector <Database> dbList;
string error;
};
DBMS::DBMS()
{
}
void DBMS::addDatabase(string tbNames)
{
vector<string> TB_Names = tokenize(tbNames);
int size = TB_Names.size();
for (int i = 0; i < size; i++)
{
if (getDatabaseIndex(TB_Names[i]) == -1)
{
Database tb(TB_Names[i]);
dbList.push_back(tb);
}
else
throw "Already esited Database with given name";
}
}
Database& DBMS::getDatabase(string tbName)
{
int i;
int size = dbList.size();
for (i = 0; i < size; i++)
{
if (dbList[i].getName() == tbName)
return dbList[i];
}
throw invalid_argument("Database not found");
}
Database& DBMS::getDatabaseByIndex(int index)
{
return dbList[index];
}
void DBMS::removeDatabase(string TB_Name)
{
int i;
int size = dbList.size();
for (i = 0; i < size; i++)
{
if (dbList[i].getName() == TB_Name)
{
dbList.erase(dbList.begin() + i);
break;
}
}
if (i == size)
throw invalid_argument("Field not found");
}
int DBMS::getDatabaseIndex(string TB_Name)
{
int size = dbList.size();
for (int i = 0; i < size; i++)
{
if (dbList[i].getName() == TB_Name)
return i;
}
return -1;
}
int DBMS::size()
{
return dbList.size();
}
DBMS::~DBMS()
{
}
(Database type is just another class i create. Nothing special about it. Don't worry about it (Unless you think I have to))
The error statement is : >a reference of type "DBMS &" (a non-const-qualified) cannot be initialized with an value of "DBMS()"
I found a suggestion that i should fix void Home(DBMS &dbms) to void Home(const DBMS &dbms)
but if i do that, i can't use addDatabase() function
How can i fix this?
This declaration
DBMS dbms();
is a vexing parse. You are not declaring a variable named dbms, but instead you are actually declaring a function named dbms that takes no arguments, and returns a DBMS. Passing this object to a function expecting a DBMS object will not work.
You can fix this with:
DBMS dbms{};
Related
class A
{
int id;
public:
A (int i) { id = i; }
void show() { cout << id << endl; }
};
int main()
{
A a[2];
a[0].show();
a[1].show();
return 0;
}
I get an error since there is no default constructor.However thats not my question.Is there a way that ı can send parameters when defining
A a[2];
A good practice is to declare your constructor explicit (unless it defines a conversion), especially if you have only one parameter. Than, you can create new objects and add them to your array, like this :
#include <iostream>
#include <string>
class A {
int id;
public:
explicit A (int i) { id = i; }
void show() { std::cout << id << std::endl; }
};
int main() {
A first(3);
A second(4);
A a[2] = {first, second};
a[0].show();
a[1].show();
return 0;
}
However, a better way is to use vectors (say in a week you want 4 objects in your array, or n object according to an input). You can do it like this:
#include <iostream>
#include <string>
#include <vector>
class A {
int id;
public:
explicit A (int i) { id = i; }
void show() { std::cout << id << std::endl; }
};
int main() {
std::vector<A> a;
int n = 0;
std::cin >> n;
for (int i = 0; i < n; i++) {
A temp(i); // or any other number you want your objects to initiate them.
a.push_back(temp);
a[i].show();
}
return 0;
}
I have been attempting to write this program where I am required to utilize dynamically allocated arrays to print out a 2d matrix. I am only to write the cpp files and not allowed to modify anything in the header files.
I keep getting an exception
0 [main] review2_cis17c_objectarray 4018 cygwin_exception::open_stackdumpfile: Dumping stack trace to review2_cis17c_objectarray.exe.stackdump
I am relatively new to learning c++; after contemplating, I think something is wrong in my PlusTab.cpp, where I am trying to assign an allocated address to a constructor-defined array in a class. Can someone please help and let me know here I did wrong in the project? Thank you very much!
AbsRow.h:
class AbsRow {
protected:
int size;
int *rowData;
public:
virtual int getSize()const = 0;
virtual int getData(int)const = 0;
};
AbsTabl.h:
class AbsTabl {
protected:
int szRow;
int szCol;
RowAray **columns;
public:
virtual int getSzRow()const = 0;
virtual int getSzCol()const = 0;
virtual int getData(int,int)const = 0; };
PlusTab.h
class PlusTab:public Table {
public:
PlusTab(unsigned int r,unsigned int c):Table(r,c){};
PlusTab operator+(const PlusTab &);
};
RowAray.h
class RowAray:public AbsRow {
public:
RowAray(unsigned int);
virtual ~RowAray();
int getSize()const{return size;}
int getData(int i)const{
if(i>=0&&i<size)return rowData[i];
else return 0;}
void setData(int,int);
};
Table.h
#include "AbsTabl.h"
class Table:public AbsTabl {
public:
Table(unsigned int,unsigned int);
Table(const Table &);
virtual ~Table();
int getSzRow()const {return szRow;}
int getSzCol()const {return szCol;}
int getData(int,int)const;
void setData(int,int,int);
};
PlusTab.cpp:
#include "PlusTab.h"
PlusTab PlusTab::operator+(const PlusTab &t) {
PlusTab tab(this->getSzRow(), this->getSzCol());
for(int i = 0; i < tab.getSzRow(); i++) {
for (int j = 0; j <tab.getSzCol(); j++) {
(tab.columns[i])->setData(j, this->getData(i,j) + t.getData(i,j));
}
}
return tab;
}
RowAray.cpp:
#include "RowAray.h"
RowAray::RowAray(unsigned int c) {
size = c;
rowData = new int[c];
}
RowAray::~RowAray() {
delete []rowData;
}
void RowAray::setData(int i, int value) {
rowData[i] = value;
}
Table.cpp:
#include "Table.h"
#include <cstdlib>
Table::Table(unsigned int r, unsigned int c) {
szRow = r;
szCol = c;
columns = new RowAray*[r];
for (int i = 0; i < r; i++) {
columns[i] = new RowAray(c);
}
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
columns[i]->setData(j, (rand()%90 + 10));
}
}
}
Table::~Table() {
for (int i = 0; i < szRow; i++) {
delete []columns[i];
}
delete []columns;
}
Table::Table(const Table &t) {
szRow = t.szRow;
szCol = t.szCol;
columns = t.columns;
};
int Table::getData(int r ,int c) const {
return columns[r]->getData(c);
};
void Table::setData(int r, int c, int value) {
columns[r]->setData(c,value);
}
and finally my main.cpp, which I am not allowed to modify either.
#include <ctime>
#include <iostream>
#include <iomanip>
using namespace std;
//User Libraries
#include "PlusTab.h"
//Global Constants
//Function Prototype
void prntTab(const Table &);
//Execution Begins Here!
int main(int argc, char** argv) {
//Initialize the random seed
srand(static_cast<unsigned int>(time(0)));
//Declare Variables
int rows=3,cols=4;
//Test out the Tables
PlusTab tab1(rows,cols);
PlusTab tab2(tab1);
PlusTab tab3=tab1+tab2;
// Print the tables
cout<<"Abstracted and Polymorphic Print Table 1 size is [row,col] = ["
<<rows<<","<<cols<<"]";
prntTab(tab1);
cout<<"Copy Constructed Table 2 size is [row,col] = ["
<<rows<<","<<cols<<"]";
prntTab(tab2);
cout<<"Operator Overloaded Table 3 size is [row,col] = ["
<<rows<<","<<cols<<"]";
prntTab(tab3);
//Exit Stage Right
return 0;
}
void prntTab(const Table &a){
cout<<endl;
for(int row=0;row<a.getSzRow();row++){
for(int col=0;col<a.getSzCol();col++){
cout<<setw(4)<<a.getData(row,col);
}
cout<<endl;
}
cout<<endl;
}
I apologize for this massive amount of code. This is my first time posting, will learn to use the website! I appreciate your help:)
I'm working with c++ STL vectors, and have a vector of structures called projectileList. I'm trying to iterate through the vector, getting and setting values in the struts as I iterate, but my code refuses to compile, with the error 'Incomplete type is not allowed.'
Can anyone please point out what I'm doing wrong:
Code:
ProjectHandeler.h:
#include "stdafx.h"
#include "DataTypes.h"
#include <vector>
class ProjectileHandeler {
private:
int activeObjects;
std::vector<projectile> projectileList;
void projectileUpdater();
public:
ProjectileHandeler(projectile* input[], int projectileCount);
~ProjectileHandeler();
};
#endif
projectileHandeler.cpp
#include "stdafx.h"
#include "DataTypes.h"
#include "ProjectHandeler.h"
#include <vector>
ProjectileHandeler::ProjectileHandeler(projectile* input[], int projectileCount)
{
for (int i = 0; i < projectileCount; i++)
{
projectileList.push_back(*input[i]);
activeObjects += 1;
}
//NO extra slots. Not that expensive.
projectileList.resize(projectileList.size());
}
void ProjectileHandeler::projectileUpdater()
{
while (true)
{
for (unsigned int i = 0; i < projectileList.size(); i++)
{
if (projectileList[i].isEditing == true)
break;
}
}
}
This compiles fine (tested it here: http://codepad.org/cWn6MPJq):
#include <vector>
struct projectile {
bool isEditing;
};
class ProjectileHandeler {
private:
std::vector<projectile> projectileList;
void projectileUpdater()
{
//This bit loops to infinity and beyond! ...or at least untill the handeler is destroyed.
while (true)
{
for (unsigned int i = 0; i < projectileList.size(); i++)
{
if (projectileList[i].isEditing == true) //Throws Incomplete type error
break;
}
}
}
};
int main()
{
}
Notice the removal of *, correct type of loop variable and removal of extra class specifier.
It seems the attribute test aisbn is successfully storing the data invoking setCode(), setDigit(). But The trouble starts failing while I attempt these values to store into list<test> simul
The list attribute takes the value of digit after setDigit() but the code. How can I put both code and digit into the list attribute? I can't see where the problem is. The code:
#include <iostream>
#include <stdlib.h>
#include <string>
#include <fstream>
#include <list>
using namespace std;
class test
{
private:
string code;
int digit;
public:
//constructor
test(): code(""), digit(0) { }
//copy constructor
test(const test &other):
digit(other.digit)
{
for(unsigned int i=0; i < code.length(); i++)
code[i] = other.code[i];
}
//set up the private values
void setCode(const string &temp, const int num);
void setCode(const string &temp);
void setDigit(const int &num);
//return the value of the pointer character
const string &getCode() const;
const unsigned int getDigit() const;
};
const string& test::getCode() const
{
return code;
}
const unsigned int test::getDigit() const
{
return digit;
}
void test::setCode(const string &temp, const int num)
{
if((int)code.size() <= num)
{
code.resize(num+1);
}
code[num] = temp[num];
}
void test::setCode(const string &temp)
{
code = temp;
}
void test::setDigit(const int &num)
{
digit = num;
}
int main()
{
const string contents = "dfskr-123";
test aisbn;
list<test> simul;
list<test>::iterator testitr;
testitr = simul.begin();
int count = 0;
cout << contents << '\n';
for(int i=0; i < (int)contents.length(); i++)
{
aisbn.setCode(contents);
aisbn.setDigit(count+1);
simul.push_back(aisbn);
count++;
}
cout << contents << '\n';
/*for(; testitr !=simul.end(); simul++)
{
cout << testitr->getCode() << "\n";
}*/
}
It looks like you are having issues with your for loop, you need to modify your for loop like so:
for(testitr = simul.begin(); testitr !=simul.end(); testitr++)
^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^
although, push_back does not invalidate iterators for std::list I think it is more readable to set the iterator where you are using it. Based on your response you also need to modify the copy constructor:
test(const test &other): code(other.code), digit(other.digit) {}
^^^^^^^^^^^^^^^^
how about using the vector
std::vector<test> simul;
for(int i=0; i < (int)contents.length(); i++)
{
aisbn.setCode(contents);
aisbn.setDigit(count+1);
simul.push_back(aisbn);
count++;
}
iterators, pointers and references related to the container are invalidated.
Otherwise, only the last iterator is invalidated.
I want to know is there something wrong in passing in passing vector reference to a function as in the example below. This code is running well and nice. But the same type of code in my project gives me crash. I don't know why.
In that case whenever I calls the function which need std::vector & . then in the called function the size of the vector reaches some millionsss.... I have attached screenshot where I am actually getting this crash.
I just wants to know is there something wrong in these type of implementations...
#include <iostream>
#include <vector>
#include <string>
class A {
public:
A() {}
~A() {}
void GetVector(std::vector<std::wstring> &in) {
std::wstring s = L"Hello";
for(int i = 0; i < 10; i++)
in.push_back(s);
}
};
class B {
public:
B() {}
~B() {}
void GetData() {
A a;
std::vector<std::wstring> s;
a.GetVector(s);
}
};
int main() {
B b;
b.GetData();
return 0;
}
Real code where I am getting the crash...
void SCPreferenceComp::PopulateComboBox()
{
SCConfig *config = SCConfig::GetInstance();
std::vector<std::wstring> languages;
config->GetAllLangugesName(languages);
for(size_t i = 0; i != languages.size(); i++)
mLangListComboBox->addItem(languages[i].c_str(), i+1);
if(mLangListComboBox->getNumItems() > 0)
mLangListComboBox->setSelectedId(1);
}
bool SCConfig::GetAllLangugesName(std::vector<std::wstring> &outLangNames)
{
bool retVal = false;
do
{
if(!mXMLDoc)
break;
xercesc::DOMNodeList *langNodeList = mXMLDoc->getElementsByTagName(strToX("language"));
if(!langNodeList)
break;
const XMLSize_t langCount = langNodeList->getLength();
for(XMLSize_t i = 0; i < langCount; i++)
{
xercesc::DOMNode *curLangNode = langNodeList->item(i);
if(!curLangNode)
continue;
xercesc::DOMElement *curLangElem = dynamic_cast<xercesc::DOMElement*>(curLangNode);
if(!curLangElem)
continue;
wxString s = strToW(curLangElem->getAttribute(strToX("name")));
outLangNames.push_back(s.c_str());
}
retVal = true;
}while(false);
return retVal;
}
I can't see anything wrong in that implementation other than the fact that it doesn't have any visible end result which leads me to believe it may not exactly match your failing code.