CODEWITHSUNDEEP
c++c++11c++14
Cameron121341
Cameron121341

Reputation: 260

Best way to copy a vector

I have a struct Y with a vector of type X, I would like to ask whether in this case assign is the best solution or copy would be better? Should I resize y.xVec?

#include <iostream>
#include <vector>

struct X {
  X(int x):x_(x)
  {}
  int x_;
};

struct Y {
  std::vector<X>xVec;
};

int main()
{
    X x1(1);
    X x2(2);
    std::vector<X> v = {x1,x2};
    
    Y y;
    y.xVec.assign(v.begin(), v.end());
    return 0;
}

Upvotes: 1

Views: 134

Answers (1)

John Zwinck
John Zwinck

Reputation: 249552

The simplest code is the best here:

y.xVec = v;

Or if you don't need v anymore:

y.xVec = std::move(v);

Or if you will use v again but starting from empty:

y.xVec = std::exchange(v, {});

exchange() is better than move() if you need to use v again, because it leaves v in its default-constructed state (empty), rather than the unspecified state given by move().

Upvotes: 1

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