How to pass struct to a class in c++? [closed] - c++

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I'm getting these results:
constructor
setFunc
setFunc
Basically I want my class-object globally and pass the struct array to setMethod of the class. and Program is successfully compiling but not getting any results.
DataInput.h
#ifndef DATAINPUT_H_
#define DATAINPUT_H_
#include <stdio.h>
struct Data{
const char *name;
int salary;
void set(int salary, const char *name){
printf("setFunc \n");
this->name = name;
this->salary = salary;
}
};
This class in a seprate cpp file with above header file
class DataInput {
public:
int dataSize;
struct Data data[];
DataInput();
virtual ~DataInput();
void setData(struct Data d[], int numberOfData);
void printData();
private:
};
#endif
-------eof----------
DataInput.cpp
#include "DataInput.h"
DataInput::DataInput() {
printf("constructor \n");
dataSize = 0;
}
DataInput::~DataInput() {
}
void DataInput :: setData(struct Data d[], int numberOfData){
dataSize = numberOfData;
for (int i = 0; i< numberOfData; i++){
printf("i-val in setData() --> %d",i);
this->data[i] = data[i];
}
}
void DataInput::printData(){
for (int i = 0; i< dataSize; i++){
printf("name--> %s \n",data[i].name);
printf("salary--> %d \n",data[i].salary);
}
}
--------eof-----------
main.cpp
#include <stdlib.h>
#include "DataInput.h"
#include <stdio.h>
DataInput *dataInput;
int main(void) {
DataInput in;
dataInput = &in;
struct Data d[2];
d[0].set(1000, "ABC");
d[1].set(2000, "XYZ");
dataInput->setData(d, 2); //not setting data
dataInput->printData(); //not printing
return 0;
}

Answer 1

Note: May not compile, is just illustrative
Few things:
DataInputconstructor do not reserve space for new items. So, this->data[i] = data[i]; result is undefined.
This is C++, Rule of three, strings, ....
struct Data
{
std::string name;
int salary;
Data(const std::string & n, int s);
Data & operator=(const Data & d);
};
Data::Data(const std::string & n, int s) :
name(n), salary(s)
{
}
Data & Data::operator=(const Data & d)
{
name = d.name;
salary = d.salary;
return *this;
}
Use standards containers:
class DataInput
{
private:
std::vector<Data> data;
public:
DataInput();
virtual ~DataInput();
// you don't need use size
void setData(const std::vector<Data> & d);
void printData();
};
void DataInput::setData(const std::vector<Data> & d)
{
data = d;
}
void DataInput::printData()
{
for (std::vector<Data>::iterator it = data.begin(); it != data.end(); ++it)
{
std::cout << it->name << ":" << it->salary << std::endl;
}
}
Now, you can use it from main (without pointers):
int main(void)
{
DataInput in;
std::vector<Data> d;
d.push_back(Data(1000, "ABC"));
d.push_back(Data(2000, "XYZ"));
dataInput.setData(d); // yes setting data
dataInput.printData(); // yes printing
return 0;
}

Answer 2

Do a memcpy of the entire array, just assigning the data might lead to memory leaks due to stack frame removal or deletion. This way however you lose the logging simultaneously avoiding the for loop increasing performance
void DataInput :: setData(const struct Data const* d, const int numberOfData) {
// Cleanup old data!
if(this->data) delete [] this->data;
if(!d) throw new std::invalid_argument("Cannot set NULL data!"); // Remove this line if NULL may be assigned and replace with the commented code.
// if(!d) {
// this->data = NULL;
// this->dataSize = 0;
// } else {
this->data = new Data[(this->dataSize = numberOfData)];
memcpy(this->data, d, sizeof(struct Data) * numberOfData);
// }
}
Don't forget to update the DataInput class!
class DataInput {
public:
int dataSize;
struct Data* data;
DataInput();
virtual ~DataInput();
void setData(const struct Data const* d, const int numberOfData);
void printData();
private:
};
void DataInput::printData() {
for (int i = 0; i< this->dataSize; i++){
printf("name--> %s \n",this->data[i].name);
printf("salary--> %d \n",this->data[i].salary);
}
}
DataInput::~DataInput() {
if(this->data) delete [] this->data;
}