I'm having an issue initializing std::array with variable.

std::string str = "Hello world this is just testing";

int size = str.size();

std::array<char, size> arr;

Returns following error:

note: 'int size' is not const
error: the value od 'size' is not usable in a constant expression
note: in template argument for type 'long long unsigned int'

I'm newbie, please help.

CodePudding user response：

You cannot use variables as template arguments unless they are compile time constant. Hence, the size of std::array must be compile time constant. What you're trying to do is not possible. Same limitation applies to array variables as well.

std::string already internally owns a dynamic array of char, so you probably don't need std::array at all.

CodePudding user response：

You need to pass a constant expression as the size to the array data structure. If you want to assign variable length to a data structure, you can use std::vector<char> v(size); instead of an array. I also think you can use variable length with arrays if you use the GCC compiler