在C ++中相同类型的向量中使用类的构造函数

Question

Consider:

MyClass {
    //constructor
    MyClass()
    {}
.
.
.
};

Then, defining a vector of the same type

int main()
{
.
.
    vector<MyClass>myVector(12);
.
.

Is this allowed?

for(int i = 0; i < myVector.size(); i++)
{
    //an attempt to fill my vector with initialized MyClass objects.
    myVector[i] = MyClass(); //Calling constructor
}

OR: (in the case of not defining a vector's size)

for(int i = 0; i < whatever; i++)
{
    //an attempt to fill my vector with initialized MyClass objects.
    myVector.push_back(MyClass()); //Calling constructor
}

If this is not allowed, what is an alternative for initializing class instances and storing them in a vector without using pointers? Is there such a thing?

Answer 1

Everything you wrote is acceptable.

vector<MyClass>myVector(12);

will call default constructor of MyClass 12 times. So this is equivalent to

vector<MyClass>myVector;
for(int i = 0; i < 12; i++)
{
    myVector.push_back(MyClass());
}

Another variant you provided is slightly different

for(int i = 0; i < myVector.size(); i++)
{
    myVector[i] = MyClass();
}

Here every element of vector is already initialized somehow. So when you do this, previous instance of MyClass will be removed (destructor will be called) and element will be assigned to new instance.

If you need make your default constructor private and initialize class with some value you have to use next aproach:

vector<MyClass>myVector(12, MyClass(some_value));

or as you already seen

vector<MyClass>myVector;
for(int i = 0; i < 12; i++)
{
    myVector.push_back(MyClass(some_value));
}