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Re: Order of member initialization [message #58888 is a reply to message #58863]

Wed, 21 September 2022 17:42

jjacksonRIAB
Messages: 220
Registered: June 2011

Experienced Member

Derp, I just realize I should have attempted to solve your problem instead of trying to just discuss order of member initialization.

OK as far as I know order of member initialization is done in the order it appears in the class, so

struct Test {
    int a;
    int b;
    int c;
   
    Test() : a(), b(a), c(b) {
    }
};

would be proper. What would be improper is if you had them appear in a different order:

struct Test {
    int c;
    int a;
    int b;

    Test() : a(), b(a), c(b) {
    }
};

so it's incumbent upon you once you use chains of dependencies in initializer lists that you don't go moving your member variables around without considering how they'll affect the initializers.

As for how to do the class you initially asked about, which I should have answered but got carried away, try this:

#include <Core/Core.h>

using namespace Upp;

class A {
public:
    A(Array<int>&& arr) : array { pick(arr) } {
        Cout() << "Array Initial item count in A = " << array.GetCount() << "\n";
        Cout() << array << EOL;
    }
    
protected:
    Array<int> array;
};

class B : public A {
public:
    B() : A { Array<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 } } {
        Cout() << "Array Initial item count in B = " << array.GetCount() << "\n";
        Cout() << array << EOL;
    }
};

CONSOLE_APP_MAIN {
    B();
}

Pick semantics with move constructor will transfer ownership of the contents of the initialized array into the base array. and they'll be available in the derived class because the base was initialized first.

[Updated on: Thu, 22 September 2022 00:52]

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