Initializing class member (vector) in constructor via initialization list

Question

The C++11 standard gives an opportunity to initialize a vector with an initialization list like this.

vector <int> a {3, 5, 6, 2};

I am just wondering if it is possible to initialize a vector which is a member of class in a constructor via initialization list.

I looked for such a thing but I did not find it on the Internet or here on Stack Overflow, so I thought that I should ask for it. I hope that not only I, but also others will find it useful.

I do not want to make vector a static member of a class.

The class should look like this:

class Foo
{
    public:
        vector <int> myvector;
        //Here should be a constructor 
};

It could be used like this:

Foo aa{1, 2, 3, 6, 1}; // it should initialize a vector

Foo::Foo(std::initializer_list<int> init_list) : a(init_list) {} — user2486888
– user2486888, Commented Apr 12, 2016 at 9:44
For the record, this is not the "new" standard any more.. there have been 1.5 newer ones since ;) — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Apr 12, 2016 at 10:25
That's an std::initializer_list, not an initiali(s/z)er list or an "initialization list". I don't want to be pedantic for its own sake, but the Standard uses such similar terms for different things that we have no choice! — underscore_d
– underscore_d, Commented Apr 12, 2016 at 11:39

Quentin · Accepted Answer · 2016-04-12 09:47:10Z

3

Yes ! You just need to take in an std::initializer_list and initialize your vector with it.

struct Foo {
    Foo(std::initializer_list<int> l)
    : _vec{l} { }

    std::vector<int> _vec;
};

Live on Coliru

answered Apr 12, 2016 at 9:47

Quentin

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2 Comments

FieryCod Over a year ago

Big thanks for your answer it is really bizzare that I didn't find it.

Lightness Races in Orbit Over a year ago

Yep especially as the answer is right there in the "Related" questions list!

rep_movsd · Accepted Answer · 2016-04-12 09:45:00Z

1

You need to define a constructor for Foo that takes an initializer list, and pass it to the vector.

See http://en.cppreference.com/w/cpp/utility/initializer_list for an example that does exactly what you need

answered Apr 12, 2016 at 9:45

rep_movsd

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