initialize class array in initialization list c++

Question

I have this class:

class Taxi {
   Wheel myWheel[4];
public:
   Taxi();
};

and Wheel is another class contain:

class Wheel{
   int radius,
       tickness;
public:
   Wheel(int,int);
};

now, what i want to do is to initialize "myWheel[4]" in initialization list of Taxi constructor, like this:

Taxi::Taxi () :Wheel[0](5,5), Wheel[1](3,3), Wheel[2](5,5), Wheel[3](3,3) {
   cout << "Ctor of Taxi" << endl;
}

but it doesn't work and i really need some HELP, thanks :)

πάντα ῥεῖ · Accepted Answer · 2014-12-08T15:10:15.927

7

Your initialization list should look like

Taxi::Taxi () : myWheel { Wheel(5,5), Wheel(3,3), Wheel(5,5), Wheel(3,3)} {
   cout << "Ctor of Taxi" << endl;
}

See a LIVE DEMO

If you don't have a compiler compliant with the current c++ standard (c++11), there's no way to do this in the member initializer list. You have to initialize the array elements inside the constructor's body:

Taxi::Taxi () {
   cout << "Ctor of Taxi" << endl;
   myWheel[0] = Wheel(5,5);
   myWheel[1] = Wheel(3,3);
   myWheel[2] = Wheel(5,5); 
   myWheel[3] = Wheel(3,3);
}

Also note you should make Wheel a nice class then.

edited Dec 08 '14 at 15:10

answered Dec 08 '14 at 14:40

πάντα ῥεῖ

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it doesn't work :/ errors: -only '()' is allowed as initializer for array member "AutoTaxi::_taxiWheel" -expected a declaration -expected a ';' -'AutoTaxi::AutoTaxi::_taxiWheel' : cannot specify explicit initializer for arrays – Naama Dec 08 '14 at 14:56
@Naama Well, the linked demo works. Are you sure to have replicated the code correctly? I had to fix some other errors until it worked. Also note the order of declaration for `Wheel` and `Taxi`. What's your compiler version language standard flags actually? – πάντα ῥεῖ Dec 08 '14 at 14:59
2

@Naama, this requires C++11 – Chris Drew Dec 08 '14 at 14:59
It's not the same code because class taxi has more varient but without this code it's working perfectly but when i try to initialize wheel it's starting to show errors – Naama Dec 08 '14 at 15:03
@ChrisDrew what do u mean c++11? – Naama Dec 08 '14 at 15:04
1

#πάντα ῥεῖ Sorry for the ignorance but I don't know how to check compiler version. I know I'm using visual studio pro 2013 version 12.0.21 – Naama Dec 08 '14 at 15:16
2

Check this Q&A then please: [Workaround for error C2536: cannot specify explicit initializer for arrays in Visual Studio 2013](http://stackoverflow.com/questions/19877757/workaround-for-error-c2536-cannot-specify-explicit-initializer-for-arrays-in-vi). It looks like VS2013 (_supporting_ c++11 by default) is broken about this. – πάντα ῥεῖ Dec 08 '14 at 15:19
@πάνταῥεῖ thank u very much for helping me, now it's working :D – Naama Dec 08 '14 at 16:47

Some programmer dude · Answer 2 · 2014-12-08T15:03:51.137

3

You can only initialize arrays if you have a C++11 capable compiler, and then you can do

Taxi::Taxi () :myWheel{{5,5}, {3,3}, {5,5}, {3,3}} { ... }

If you don't have a C++11 capable compiler, then you have to initialize the array manually:

Taxi::Taxi()
{
    myWheel[0] = Wheel(5, 5);
    myWheel[1] = Wheel(3, 3);
    myWheel[2] = Wheel(5, 5);
    myWheel[3] = Wheel(3, 3);
}

edited Dec 08 '14 at 15:03

answered Dec 08 '14 at 14:41

Some programmer dude

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doesn't work as well.. error: cannot specify explicit initializer for arrays – Naama Dec 08 '14 at 14:58
1

I don't think the second variant is legal C++. – juanchopanza Dec 08 '14 at 15:01
Everyone are correct, it was not valid in pre-C++11. Updated my answer – Some programmer dude Dec 08 '14 at 15:05

initialize class array in initialization list c++

2 Answers2