CODEWITHSUNDEEP
c++objectinitialization
joey
joey

Reputation: 19

Initializing objects in c++

There are multiple ways of initializing an object in c++. There are two examples below, ent1 and ent2. I'm wondering what the difference is, and is one of them more 'correct' or preferred over another?

class Entity {
public:
    int h;
    Entity(int health) : h(health) { }
}

Entity ent1(10);

Entity ent2 = Entity(10);

Upvotes: 0

Views: 74

Answers (1)

Kon
Kon

Reputation: 4099

In C++17, both of these are identical. Pre C++17, however, there is a subtle difference as follows:

The one below is a copy constructor. This will create an anonymous Entity and then copy over to ent2, although the copy may be omitted subject to copy epsilon.

Entity ent2 = Entity(10);

The one below is a direct instantiation, the memory for ent1 will be allocated and value 10 will be placed in the area specified by the constructor.

Entity ent1(10);

The reason direct is preferred, in pre C++17, is because it doesn't require the extra copy step. This advantage is non-existent in C++17.

Upvotes: 2

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