CODEWITHSUNDEEP
c++classvector2ddefault
Kang_HM
Kang_HM

Reputation: 13

c++ initialize 2d vector with a new class ; default value change

I would like to initialize a 2d vector but I keep getting an error message

if I write this code 

unsigned long size = 101;
double initialmPo = 63;

std::vector<std::vector<Soil> > matrixPotential(
              size, std::vector<Soil>(size));

I do not have a problem but if I write this code 

    std::vector<std::vector<Soil> > matrixPotential(
              size, std::vector<Soil>(size, initialmPo));

I get the message of

no matching constructor for initialization of  std::vector< Soil >

I would like to have a 101*101 vector and inside of vector is the value(number) of 63.

And that is my class Soil 

class Soil
{
public:
    Soil();
    double A;
    double B;
    double C;
    double D;
};

#endif // SOIL_H

What should I do?

Upvotes: 0

Views: 154

Answers (1)

francesco
francesco

Reputation: 7539

Your code does not work because initialmPo is not a valid Soil instance. The constructor of std::vector you need is

explicit vector( size_type count,
                 const T& value = T(),
                 const Allocator& alloc = Allocator());     (until C++11)

         vector( size_type count,    
                 const T& value,
                 const Allocator& alloc = Allocator());     (since C++11)

For this to work you should pass the desired Soil element as a second parameter. In your class, you should define a constructor that takes care of initializing the fields with the desired value(s). Or you should eliminate the parameterless constructor and opt for an aggregate initialization.

Example (with constructor)

#include <vector>

class Soil
{
public:
    double A;
    double B;
    double C;
    double D;
    Soil(double in) : A{in}, B{in}, C{in}, D{in} { }
};


int main()
{
  unsigned long size = 101;
  double initialmPo = 63;
  Soil s(initialmPo);
  std::vector<std::vector<Soil> > matrixPotential(
              size, std::vector<Soil>(size, s));

  return 0;
}

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Example (with aggregate initialization)

#include <vector>

class Soil
{
public:
    double A;
    double B;
    double C;
    double D;
};


int main()
{
  unsigned long size = 101;
  double initialmPo = 63;
  Soil s{initialmPo, initialmPo, initialmPo, initialmPo};
  std::vector<std::vector<Soil> > matrixPotential(
              size, std::vector<Soil>(size, s));

  return 0;
}

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Upvotes: 1

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