Array of inherited object from abstract class C++

Question

I am trying to make an array of different objects that are all inherited from one abstract class. Is this possible? Here's what I have:

Human *human;
human = new Human(100,100);

Cyberdemon *cyberDemon;
cyberDemon = new Cyberdemon(100, 100);

Balrog *balrog; 
balrog = new Balrog(100, 100);

Elf *elf;
elf = new Elf(100, 100);

Human and Elf get inherited from Creature which is an abstract class. Cyberdemon and Balrog get inherited from Demon class which inherits also from Creature. What is the best way to make an array of these four objects?

You can't make an array of the objects themselves, but you can make an array of object pointers. — Mark Ransom
– Mark Ransom, Commented May 1, 2014 at 16:45
You can probably make an array of Creature objects and cast them individually to their subclass, then get type for each object. — La-comadreja
– La-comadreja, Commented May 1, 2014 at 16:46
Anything against Creature ** theArray = {human, cyberDemon, balrog, elf};? (Sorry, forgot the variable name...) — João Mendes
– João Mendes, Commented May 1, 2014 at 16:47

iavr · Accepted Answer · 2014-05-01 17:29:59Z

4

Because I like code to be tidy:

Human      *human      = new Human(100, 100);
Cyberdemon *cyberDemon = new Cyberdemon(100, 100);
Balrog     *balrog     = new Balrog(100, 100);
Elf        *elf        = new Elf(100, 100);

std::vector<Creature*> creatureList{human, cyberDemon, balrog, elf};

Or, if you won't be needing individual pointers later:

std::vector<Creature*> creatureList{
    new Human(100, 100),
    new Cyberdemon(100, 100),
    new Balrog(100, 100),
    new Elf(100, 100)
};

Or, tidy and safe (thanks Kerrek SB):

std::vector<unique_ptr<Creature>> creatureList{
    std::make_unique<Creature>(100, 100),
    std::make_unique<Cyberdemon>(100, 100),
    std::make_unique<Balrog>(100, 100),
    std::make_unique<Elf>(100, 100)
};

edited May 1, 2014 at 17:29

answered May 1, 2014 at 16:51

iavr

7,6671 gold badge21 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

justin henricks Over a year ago

ahh the vector, was thinking I would need to use that. Thank you I appreciate it!

iavr Over a year ago

@KerrekSB Well, tidy except for that... I took the pointers as granted and looked only at the "make an array of different objects" problem :-)

iavr Over a year ago

@KerrekSB Added another version.

Kerrek SB Over a year ago

@iavr: Neat, though it isn't exception safe and probably doesn't compile, on account of explicit constructors.

Apriori Over a year ago

@Kerrek SB:I realize this is probably where you were going with this but one could make this exception safe if one provides an implementation for make_unique as described here: stackoverflow.com/questions/7038357/… (making it a hyperlink wasn't working, look at the link in the chosen answer). However, this is probably outside the scope of OPs question, and somewhat of an advanced topic, especially if OP is just learning C++ polymorphism.

|

R Sahu · Accepted Answer · 2014-05-01 16:55:11Z

3

std::vector<Creature*> creatureList;

Human *human;
human = new Human(100,100);
createList.push_back(human);

Cyberdemon *cyberDemon;
cyberDemon = new Cyberdemon(100, 100);
createList.push_back(cyberDemon);

Balrog *balrog; 
balrog = new Balrog(100, 100);
createList.push_back(barlog);

Elf *elf;
elf = new Elf(100, 100);
createList.push_back(elf);

Or, a little bit simplified:

std::vector<Creature*> creatureList;

createList.push_back(new Human(100,100));
createList.push_back(new Cyberdemon(100, 100));
createList.push_back(new Balrog(100, 100));
createList.push_back(new Elf(100, 100));

If you are able to use C++11, you can simplify it a little further (thanks Chnossos).

std::vector<Creature*> creatureList = { new Human(100,100), 
                                        new Cyberdemon(100, 100),
                                        new Balrog(100, 100),
                                        new Elf(100, 100) };

edited May 1, 2014 at 16:55

answered May 1, 2014 at 16:48

R Sahu

207k15 gold badges168 silver badges291 bronze badges

4 Comments

Chnossos Over a year ago

I would post a C++11 version too, like

std::vector<Creature *> creatureList = { new Human(100, 100), new Cyberdemon(100, 100), new Balrog(100, 100), new Elf(100, 100) };

Apriori Over a year ago

@Chnossos: I think you need to remove the = before the brace.

R Sahu Over a year ago

@Apriori Both forms are valid. What you suggest is direct initialization while what I have in the answer is copy initialization.

Apriori Over a year ago

@R Sahu: Thank you for the clarification. I am reading about the syntax now, so far the article has only said there is no =. I appreciate the supplementary knowledge.

Collectives™ on Stack Overflow

Array of inherited object from abstract class C++

2 Answers 2

7 Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

7 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related