What is the use of a constructor? [closed] - c++

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I dont exactly get the use of a constructor
For example:
class car
{
public:
string name;
long int price;
int mileage
bool ownedByPlayer;
};
Here, why will I use a constructor like this,
class car
{
public:
string name;
long int price;
int mileage
bool ownedByPlayer;
car()
{
ownedByPlayer = false;
}
};
if I can simply define the variable ownedByPlayer where I have declared it. Like: bool ownedByPlayer = false; ?

Answer 1

In your case there is no need to write the constructor. Actually it is recommended to not write a constructor that does nothing but initialize members with default values. Though the correct way would be to use the member initializer list:
car() : ownedByPlayer(false) {}
And since C++11 you can use a default member initializer instead:
class car {
// ...
bool ownedByPlayer = false;
// ...
};
Sometimes constructors actually need to do something. Consider a car registers itself somewhere after being constructed, then your class could look like this:
class car
{
public:
string name;
long int price;
int mileage;
car(string name,long int price, int mileage) : name(name),price(price),mileage(mileage) {
CarRegistrationFacility::register_car(*this);
}
};
Actually I found it difficult to make up an example for a constructor that does more than initializing members, because thats what constructors do. However, when your constructor does more than that, then that "more" happens in the body of the constructor.