How can I initialize an array of objects?

Question

I've written this code but I have some errors when I try to initialize an array of Critter objects and don't know what they're about.

My code:

#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Critter {
private:
    string crName;
public:
    Critter(string = "Poochie");
    string getName() const { return crName; }
};

Critter::Critter(string n) {
    crName = n;
}

int main() {
    Critter c[10] = { "bob","neo","judy","patrik","popo" }; //here
    return 0;
}

The errors:

E0415 - no suitable constructor exists to convert from "const char [4]" to "Critter"
...
4 more like this.

This code worked on a friend's Visual Studio 2017, but not in mine which is the 2019 version.

Thanks.

Plenty of fine answers already, but yet another way to initialize it would be to put `using namespace std::literals::string_literals;` in scope, then do `Critter c[10] = { "bob"s, "neo"s, "judy"s, "patrik"s, "popo"s };` — aschepler, Jun 15 '20 at 19:15

anastaciu · Answer 1 · 2020-06-15T20:20:50.513

The initialization you have is for an array of strings, for the objects you need:

Critter c[10] = {Critter("bob"), Critter("neo"), Critter("judy"),
                 Critter("patrik"), Critter("popo")};

Or

Critter c[10] = {{"bob"}, {"neo"}, {"judy"}, //(*)
                 {"patrik"}, {"popo"}};

*This second method is credited to @drescherjm comment followed by @dxiv's answer, both mentioned it first.

This second initialization may be what your friend used, and maybe you forgot the braces, the IDE version difference doesn't seem relevant here.

Note that C++ provides a container for fixed size arrays, std::array:

std::array<Critter, 10> c = {Critter("bob"), Critter("neo"),
                             Critter("judy"), Critter("patrik"), Critter("popo")};

On a side note:

You should avoid using namespace std;

dxiv · Accepted Answer · 2020-06-15T19:22:55.070

Critter c[10] = { "bob","neo","judy","patrik","popo" };

This defines an array of const char *. To initialize an array of Critter with those strings, instead:

Critter c[10] = { {"bob"}, {"neo"}, {"judy"}, {"patrik"}, {"popo"} };

[ EDIT ] It was pointed out that the same answer was first posted in a comment, only it was hidden in an external link with no indication of what's behind it, which I did not see before posting the above. Credit goes to @drescherjm so I'll leave this here as a CW.

score 0 · Answer 3 · answered Jun 15 '20 at 17:59

string c[10] = {"bob","neo","judy","patrik","popo"}; Would be correct.

{"bob","neo","judy","patrik","popo"} is an array containing string elements.

You need to do

Critter c[10]={ Critter("bob"),Critter("neo"),Critter("judy"),Critter("patrik"),Critter("popo")};

score -1 · Answer 4 · answered Jun 15 '20 at 18:01

C++ only allows one "user-defined conversion" at a time.

You're providing char const[N]s (let's call them char const*s for the sake of argument), which need to be turned into std::strings (which count as "user-defined" in this context), which need to be turned into Critters.

That's two conversions, not one.

That's just a limitation of C++, I'm afraid. You'll have to temporarily instantiate either strings or Critters within that initialiser.

How can I initialize an array of objects?

4 Answers4