Question

这是我的代码：

class package
{
protected:
    string name;
    string city;
    string state;
    int zip;
    double weight;
    double costPerOunce;

public:

    package::package(string Name, string City, string State, int Zip, double Weight, double CostPerOunce):
      name(Name), city(City), state(State),
      zip(Zip), weight(Weight), costPerOunce(CostPerOunce)
      {

      }
      double calculateCost()
    {
        return (weight * costPerOunce);
    }

};
class twoDayPackage: public package
{
protected:
    double flatFee;
public:
    twoDayPackage::twoDayPackage(double FlatFee):
      flatFee(FlatFee)
      {

      }
    double calculateCost()
    {
        return (weight * costPerOunce) + flatFee;

    }
};
int main()
{


    system ("pause");
    return 0;
}

我尝试运行此代码，我得到的错误如下：错误C2512：'package'：没有合适的默认构造函数

错误与基类构造函数的继承有关，但我不确切知道代码未运行的原因。请帮帮我。

Answer 1

twoDayPackage::twoDayPackage(double FlatFee):
  flatFee(FlatFee)

正在调用基础构造函数package()，因为您尚未指定任何其他内容。

在课程包中添加一行package::package(){};：）

Answer 2

你需要一个包的构造函数。同样，在声明构造函数时也不需要package::package(...)（这是在cpp文件中定义的时候。）只需package(...)即可。

class package
{
protected:
    string name;
    string city;
    string state;
    int zip;
    double weight;
    double costPerOunce;

public:
    package()
    {}
    // \/ You don't need package:: that's only needed when you define the func in cpp
    package(
        string Name, string City, string State, int Zip, 
        double Weight, double CostPerOunce
    )
        : name(Name), city(City), state(State),
        zip(Zip), weight(Weight), costPerOunce(CostPerOunce)
    {

    }
    double calculateCost()
    {
        return (weight * costPerOunce);
    }

};

Answer 3

在构建twoDayPackage之前，package的构造函数将首先创建flatFee。由于你没有告诉它如何做到这一点，它寻找一种构建package的默认方式。

构建twoDayPackage时，您需要为构建基础package提供所需的一切。要么是，要么确定要传递给package构造函数的值。

传递所需的参数如下所示：

class twoDayPackage {
public:
    twoDayPackage(string Name, string City, string State, int Zip, double Weight, double CostPerOunce, double flatFee) :
    package(Name, City, State, Zip, Weight, CostPerOunce),
    flatFee(flatFee) {
    }
    //..
};

没有合适的默认构造函数可用错误

3 个答案: