我们如何在C ++的类构造函数中初始化std :: vector？

Question

How do we initialize a std::vector in a class constructor in c++?

class MyClass
{
public:
    MyClass( int p_Var1, int* p_Vector ) : Var1( p_Var1 ) //, Initialize std::vector - MyVector with p_Vector
    {
    };
    ~MyClass( void );
private:
    int Var1;
    std::vector< int > MyVector;
};

Answer 1

First, myVector will be initialized, even if you do nothing, since it has non-trivial constructors. If you want to initialize it given a pointer to a sequence of int , you'll also have to know the length. If you have both a pointer and the length, you can do:

: myVector( pInitialValues, pInitialValues + length )

Alternatively (and more idiomatically), you'll let the caller do the addition, and have the constructor take two pointers, a begin and an end:

: myVector( pBegin, pEnd )

(If the caller is using C++11, he can obtain these from a C style array using std::begin() and std::end() .)

EDIT:

Just to make it perfectly clear: just an int* doesn't provide enough information to do anything. An int* points to the first element of a C style array; you also need some way of finding the end: an element count, an end pointer, etc. In special cases, other techniques can be used; ie if the C style array contains only non-negative numbers, you could use -1 as a sentinal, and something like : myVector( pVector, std::find( pVector, NULL, -1 ) ) . These are special cases, however.