为什么报这个错误啊C:\Users\你的一鸣\AppData\Local\Temp\ccQPAet5.o pta002.cpp:(.text$_ZN3DogC1Ev[_ZN3DogC1Ev]+0x14): undefined reference to `Mammal::Mammal()'
还有就是函数后加const是为啥用
#include
using namespace std;
enum COLOR{ WHITE, RED, BROWN, BLACK, KHAKI };
class Mammal
{
public:
//constructors
Mammal();
Mammal(int age)
{itsAge=itsAge;
}
~Mammal();
//accessors
int GetAge() const
{
return itsAge;
}
void SetAge(int a)
{
itsAge=a;
}
int GetWeight() const
{
return itsWeight;
}
void SetWeight(int w)
{
itsWeight=w;
}
//Other methods
void Speak() const
{
cout<<"Mammal is spaeking..."<Sleep() const;
protected:
int itsAge;
int itsWeight;
};
class Dog:public Mammal
{
public:
Dog(){}
Dog(int age):Mammal(age){ }
Dog(int age,int weight):Mammal(age){itsWeight=weight;}
Dog(int age,COLOR color):Mammal(age){itsColor=color;}
Dog(int age,int weight,COLOR color):Mammal(age){itsWeight=weight;itsColor=color;}
~Dog(){}
void WagTail()
{
cout<<"The Dog is Wagging its tail..."<BegForFood()
{
}
void GetColor()
{
cout<SetColor(COLOR c)
{
itsColor=c;
}
protected:
COLOR itsColor;
};
int main()
{
Dog Fido;
Dog Rover(5);
Dog Buster(6, 8);
Dog Yorkie(3, RED);
Dog Dobbie(4, 20, KHAKI);
Fido.Speak();
Rover.WagTail();
cout << "Yorkie is " << Yorkie.GetAge()<< " years old." << endl;
cout << "Dobbie weighs " << Dobbie.GetWeight() << " pounds." << endl;
return 0;
}