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
– aschepler, Commented Jun 15, 2020 at 19:15

anastaciu · Accepted Answer · 2020-06-15 20:20:50Z

10

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;

edited Jun 15, 2020 at 20:20

answered Jun 15, 2020 at 17:57

anastaciu

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2 revs · Accepted Answer · 2020-06-15 19:22:55Z

4

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.

edited Jun 15, 2020 at 19:22

community wiki

2 revs
dxiv

Comments

EEAH · Accepted Answer · 2020-06-15 17:59:37Z

0

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")};

answered Jun 15, 2020 at 17:59

EEAH

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Comments

Asteroids With Wings · Accepted Answer · 2020-06-15 18:01:26Z

-1

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.

answered Jun 15, 2020 at 18:01

Asteroids With Wings

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