How to allocate dynamically a vector of a class?

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I am learning about dynamic memory and have a question.
Let say I have this class.

C++

class Elf {
private:
    double _health = 0;
public:
    Elf(const double &health){_health = health;}
};

I can create an Elf object using smart pointer like this.

C++

unique_ptr<Elf> vec1 = make_unique<Elf>(90);

In main, without using pointers, I make the vector using this lines.

C++

vector<Elf> vec2;
for (auto i = 0 ; i < 10000; i++){
    vec2.push_back(90);
}

I still have lots to learn.
How can I dynamically allocate a vector of Elf class?

Posted 15-Dec-15 1:43am

Are Riff

Updated 15-Dec-15 3:01am

Leo Chapiro

v2

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[no name] 15-Dec-15 8:59am

Dynamically allocating vector is trivial. Are you actually talking about making a vector of dynamically allocated Elf's i.e. a vector of pointers to Elf, which is different.

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User 59241 · Accepted Answer · 2015-12-15T03:21:00

Solution 2

From your example I am guessing you are asking how to construct the vector of unique_ptr's to Elf and populate. Like so:

C++

vector<unique_ptr<Elf>> vec_uniqptrElf;

for (auto i = 0; i < 10000; ++i) {

    vec_uniqptrElf.push_back(
        unique_ptr<Elf>(new Elf(90)));
}

Posted 15-Dec-15 3:21am

User 59241

Updated 15-Dec-15 3:28am

v4

Comments

Are Riff 15-Dec-15 10:55am

Thanks

Leo Chapiro · Accepted Answer · 2015-12-15T02:34:00

You are just doing this :)
Vector already internally dynamically allocates when you push_back into it.

If you think about something like

C++

vector<Elf> * pVec = new vector<Elf> (size);

so you don't need it: vector is already a wrapper around the process of dynamic allocating, so dynamically allocating vectors is like a double positive. It's redundant.

Take a look: http://stackoverflow.com/questions/6775643/allocating-vectors-or-vectors-of-vectors-dynamically[^]