initialize a member unique_ptr to empty

Question

In my program, I have a bunch of objects of a custom class Position. The declaration of Position is as follows: ``` class Position { public: Position(int x, int y); ~Position(); Actor *getActor() { return actor.get(); }; void setActor(Actor *actor) { actor = std::move(actor); }; Actor *clearActor() { return actor.release(); }; int getX() { return x; }; int getY() { return y; }; private: int x, y; std::unique_ptr<Actor> actor; }; ``` I also have a class called Actor. Not every Position will have an Actor, and so the majority of the time the unique_ptr "actor" of a Position object should be empty (I'm using unique_ptrs to automatically clean up any Actor associated with a Position at runtime). The Position constructor is as follows: ``` Position::Position(int x, int y) { this->x = x; this->y = y; actor.reset(nullptr); } ``` However, I know that this isn't correctly setting the stored pointer to nullptr because when I try calling actor.get() inside Position::getActor(), I get an error as…

Accepted Answer

Your error is here:

```
void setActor(Actor *actor) { actor = std::move(actor); };
```

You're assigning the result of `std::move` to the parameter `actor`. You probably meant to `reset` the member variable `actor` with the parameter `actor`:

```
void setActor(Actor *actor) { this->actor.reset(actor); };
```

As a side note, you can simply change your constructor to this:

```
Position::Position(int x, int y)
: x(x), y(y)
{
}
```

This will initialize the members `x` and `y` with the arguments, and default-initialize `std::unique_ptr<Actor> actor` to null.

initialize a member unique_ptr to empty

Solution

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