Why isn't my class constructor initializing its member variables?

MotoDave452 发表于 Dev

Eddie

Forgive me if the information is a bit lacking as I am trying to follow the recommended "Asking Guidelines".

I have created a class called "Item" to store item information and have defined my constructor as follows:

Item::Item(std::string number, std::string name, int quantity, double price) {
    itemNumber = number;
    itemName = name;
    quantity = quantity;
    unitPrice = price;
}

and I initialize it in my main function like so:

Item temp("string", "string", 0, 0);

but when I printed the values of item, only itemNumber and itemName printed correctly.all that printed was random garbage. Then I realized the issue is quantity and price aren't getting initialized. Why is that?

πάντα ῥεῖ

Try

this->quantity = quantity;

or (IMHO better):

Item::Item(const std::string& number, const std::string& name, int quantity_, double price) {
                                                          // ^
    // ...
    quantity = quantity_;
    // ...
}

or (IMHO even better) use a constructor initializer list:

Item::Item(const std::string& number, const std::string name&, int quantity, double price) 
: itemNumber(number), itemName(name), quantity(quantity), unitPrice(price) {}

" Why is that?"

The parameter name currently shadows your member variable name in the constructor's body scope.

Personally I tend to have class declarations like follows

class Item {
public:
    Item(const std::string& number, const std::string& name, int quantity, double price) 
    : itemNumber_(number)
    , itemName_(name)
    , quantity_(quantity)
    , unitPrice_(price) {}
private:
    std::string itemNumber_;
    std::string itemName_;
    int quantity_;
    double unitPrice_ 
};

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