CODEWITHSUNDEEP
c++g++
Zhi Lu
Zhi Lu

Reputation: 527

How to assign value to an array, which is a struct member?

I define the following struct

struct CCPtDist
{
  double[] wDist = new double[8];
};

And I want to build a "CCPtDist" variable called tmpPtDist and want to assign a double number to wDist:

CCPtDist tmpPtDist;
tmpPtDist.wDist[0] = 233.7;

But the g++ compiler returns an error: ‘struct CCPtDist’ has no member named ‘wDist’?

Upvotes: 2

Views: 182

Answers (3)

jogojapan
jogojapan

Reputation: 69977

If you want a fixed-size (!) array as part of your struct, there is no need for dynamic allocation (i.e. new):

struct CCPtDist
{
  double wDist[8];
};

will suffice. However, note that the 8 values of this array are not initialized this way. They will contain random garbage. So better add a constructor that initializes the array:

struct CCPtDist
{
  double wDist[8];
  CCPtDist():wDist() {}
};

If your compiler supports it, using std::array, which was introduced in C++11, might be a better approach, as described in SRN's answer.

Upvotes: 0

SRN
SRN

Reputation: 2455

As an alternative to a C-style array, you can use std::array:

#include <array>

struct CCPtDist
{
  std::array<double,8> wDist;
};

int main()
{   
  CCPtDist tmpdist;
  tmpdist.wDist[0]=233.7;
}

Upvotes: 4

Antimony
Antimony

Reputation: 39451

There are a number of things wrong in the code. First off, if you declare an array as a member, the memory is allocated inline as part of the struct. You can't just assign an arbitrary pointer to it. Second off, I don't think you declared the array correctly anyway. Third, you need to put complex initialization like that in a constructor. I'm surprised it doesn't give you a compile error on the double[] wDist = new double[8]; line.

Try changing it to something like this

struct CCPtDist
{
    double* wDist;

    CCPtDist(): wDist(new double[8]) {}
};

Upvotes: 1

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