Vector of const objects giving compile error

Question

I have declared the following in my code

vector  mylist; 

I get the following compile error -

new_allocator         


        

Answer 1

The use of the push_back method is the problem. emplace_back will compile. Another alternative (depending on the whole situation you do not describe here) would be to use a vector if the inserted items have a life outside the vector. Items in a vector do not need to be assignable, but when they are not, some member functions and algorithms can not be used.

Explanation :

push_back is supposed to first default-construct an A in the vector, then assign (using copy-construct) the given reference. This breaks your const qualification, hence does not compile.

emplace_back uses "perfect forwarding" to invoke the actual constructor directly in place.