Question

I’m trying to declare an array with a custom class. When I added a constructor to the class, my compiler complains that there’s “No matching constructor for initialization of name[3]”.

Here’s my program:

#include <iostream>

using namespace std;

class name {
  public:
    string first;
    string last;

  name(string a, string b){
    first = a;
    last = b;
  }
};

int main (int argc, const char * argv[])
{

  const int howManyNames = 3;

  name someName[howManyNames];

  return 0;
}

What can I do to make this run, and what am I doing wrong?

Answer 1

You have to provide a default constructor. While you’re at it, fix your other constructor, too:

class Name
{
public:
  Name() { }
  Name(string const & f, string const & l) : first(f), last(l) { }
  //...
};

Alternatively, you have to provide the initializers:

Name arr[3] { { "John", "Doe" }, { "Jane", "Smith" }, { "", "" } };

The latter is conceptually preferable, because there’s no reason that your class should have a notion of a “default” state. In that case, you simply have to provide an appropriate initializer for every element of the array.

Objects in C++ can never be in an ill-defined state; if you think about this, everything should become very clear.

---

An alternative is to use a dynamic container, though this is different from what you asked for:

std::vector<Name> arr;
arr.reserve(3);  // morally "an uninitialized array", though it really isn't

arr.emplace_back("John", "Doe");
arr.emplace_back("Jane", "Smith");
arr.emplace_back("", "");

std::vector<Name> brr { { "ab", "cd" }, { "de", "fg" } }; // yet another way