Initializing variable in class

Question

I need to initialize vector in class this way

vector<string> test("hello","world");

But when I do it, compiler recognize it as an function and give me errors like error: expected identifier before string constant etc.

When I do it this way

vector<string> test = ("hello","world")

it is ok.. Is there some way how to do it in vector<string> test("xx") way?

Are you sure, that vector<string> test = ("hello","world") does what you think it does? — Kiril Kirov
– Kiril Kirov, Commented Nov 30, 2012 at 18:03

Nikos C. · Accepted Answer · 2012-11-30 18:18:35Z

5

There is no such constructor in std::vector that would allow you to initialize it like that. And your second example evaluates to "world" (that's what the , operator does) which is what ends up in the vector.

If you want to initialize the vector at declaration time, use an initializer list:

vector<string> test = {"hello", "world"};

Make sure you build your source code in C++-11 mode for this to work. If you don't have a C++-11 compatible compiler, then you must add the values to the vector afterwards:

vector<string> test;
test.push_back("hello");
test.push_back("world");

edited Nov 30, 2012 at 18:18

answered Nov 30, 2012 at 18:07

Nikos C.

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4 Comments

hinafu Over a year ago

or just string arr[] = {"hello","world"}; and vector<string> test(arr,arr + 2);

Nik Bougalis Over a year ago

Actually, the comma operator doesn't do what you think it does either. His second example evaluates to "world".

user1751550 Over a year ago

string fonoArgs[] = {"1","2","3"}; vector<string> fonoS(fonoClass::fonoArgs,fonoClass::fonoArgs+3); This is giving me errors error: ‘fonoClass::fonoArgs’ is not a type

Nikos C. Over a year ago

@user1751550 I've no idea what fonoClass is supposed to be. Anyway, don't use that approach as it introduces a copy of your vector in the form of a plain array. Which is a waste. Just use an initializer list (you didn't mention what compiler you're using.)

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