Default constructor and returning by pointer

Question

I have a class Item that has a non-default constructor and doesn't have a default constructor. There is no default constructor because I don't want to have Item objects with some strange default values around.

class Item {
 int a;
public:
 Item(int a) : a(a) {}
}

Another class User uses Item class and has a method GetItem(Item * item) that returns an Item object by pointer.

class User {
 Item item;
public: 
 bool SetItem(Item item) {
 this->item = item;
 return true;
 }
 bool GetItem(Item * item) { // Can't do "Item * GetItem()"
 *item = this->item;
 return true;
 }
}

The problem is when I try to GetItem() from somewhere in my program, I still need to allocate memory for an Item object by using some random values, for example Item anotherItem(999);

User user;
Item item(5);
user.SetItem(item);
// Here is the problem
Item anotherItem(999); // any random value
user.GetItem(&anotherItem);

What is the best practice to handle such situations? Is it better to have a default constructor?

Thank you for your help in advance.

Answer 1

In a situation like yours, there are only a few real options

1. Allow creation of a default-constructed Item. This means adding a default constructor
2. Return a (pointer to a) Item from GetItem
3. Take a Item** or Item*& and let the passed Item pointer refer to the internal Item of User.

None of the options is inherently better than any of the others, although the third one has the big drawback that it allows modification of User content without going through a method of the User class. That opens up the door for violating the constrants that User tries to uphold.

• Konstantin: Thank you for your reply! Could you please explain the second option?
• Andy: @Konstantin Second options means changing the GetItem method of the User class to Item* GetItem() const { return &item; }. I added the const qualifier as a convention because the call does not modify the User object.
• Konstantin: @Bart van Ingen Schenau Thank you for the clarification.

Answer 2

You can use a pointer for the anotherValue Item. You don't have to call the constructor, you can pass it to the getItem function, you don't have to manage it, Because clearly you don't have the ownership of it.

• Konstantin: Thank you for the reply, but I'm not sure that I completely understand it.
• LaboPie: You can declare anotherValue that now is a Item as a Item* (Item pointer) in this way you can skip the constructor call.
• Konstantin: Can you provide a code sample, please?