push_back向量的新元素

Question

I have this vector:

std::vector<my_class> my_vector;

I want to add new item with the default constructor. So, I write:

my_vector.push_back(my_class());

is there way to do it without mention the type directly?. For example something like:

 my_vector.push_back(auto()); // imaginary code

Answer 1

std::vector has a member function called emplace_back which constructs a new instance of the vector's element type in the vector, from the arguments provided to the function.

So if my_class is default constructible, you can do:

my_vector.emplace_back();

Answer 2

my_vector.resize(my_vector.size() + 1);

Answer 3

如果您的类允许默认构造函数：

my_vector.push_back({});

Answer 4

my_vector.push_back(decltype(my_vector)::value_type());

Answer 5

my_vector.push_back({});

甚至更好

my_vector.emplace_back();