C++: constructor initializer for arrays

Question

I'm having a brain cramp... how do I initialize an array of objects properly in C++?

non-array example:

struct Foo { Foo(int x) { /* ... */  } };

struct Bar { 
     Foo foo;

     Bar() : foo(4) {}
};

array example:

struct Foo { Foo(int x) { /* ... */  } };

struct Baz { 
     Foo foo[3];

     // ??? I know the following syntax is wrong, but what's correct?
     Baz() : foo[0](4), foo[1](5), foo[2](6) {}
};

edit: Wild & crazy workaround ideas are appreciated, but they won't help me in my case. I'm working on an embedded processor where std::vector and other STL constructs are not available, and the obvious workaround is to make a default constructor and have an explicit init() method that can be called after construction-time, so that I don't have to use initializers at all. (This is one of those cases where I've gotten spoiled by Java's final keyword + flexibility with constructors.)

Answer 1

There is no way. You need a default constructor for array members and it will be called, afterwards, you can do any initialization you want in the constructor.

Answer 2

Just to update this question for C++11, this is now both possible to do and very natural:

struct Foo { Foo(int x) { /* ... */  } };  struct Baz {       Foo foo[3];       Baz() : foo{{4}, {5}, {6}} { } }; 

Those braces can also be elided for an even more concise:

struct Baz {       Foo foo[3];       Baz() : foo{4, 5, 6} { } }; 

Which can easily be extended to multi-dimensional arrays too:

struct Baz {     Foo foo[3][2];      Baz() : foo{1, 2, 3, 4, 5, 6} { } }; 

Answer 3

Right now, you can't use the initializer list for array members. You're stuck doing it the hard way.

class Baz {
    Foo foo[3];

    Baz() {
        foo[0] = Foo(4);
        foo[1] = Foo(5);
        foo[2] = Foo(6);
    }
};

In C++0x you can write:

class Baz {
    Foo foo[3];

    Baz() : foo({4, 5, 6}) {}
};