push_back vs emplace_back

Question

I\'m a bit confused regarding the difference between push_back and emplace_back.

void emplace_back(Type&& _Val);
void push_         


        

Answer 1

Specific use case for emplace_back: If you need to create a temporary object which will then be pushed into a container, use emplace_back instead of push_back. It will create the object in-place within the container.

Notes:

1. push_back in the above case will create a temporary object and move it into the container. However, in-place construction used for emplace_back would be more performant than constructing and then moving the object (which generally involves some copying).
2. In general, you can use emplace_back instead of push_back in all the cases without much issue. (See exceptions)