C++类继承问题

Question

嗨,我有两个类,一个叫做Instruction,一个叫做LDI,它继承自指令类.

class Instruction{

  protected:
    string name;
    int value;

  public:
    Instruction(string _name, int _value){ //constructor
        name = _name;
        value = _value;
    }
    ~Instruction(){}
    Instruction (const Instruction &rhs){
        name = rhs.name;
        value = rhs.value;
    }
    void setName(string _name){
        name = _name;
    }
    void setValue(int _value){
        value = _value;
    }
    string getName(){
        return name;
    }
    int getValue(){
        return value;
    }
    virtual void execute(){}
    virtual Instruction* Clone() { 
        return new Instruction(*this); 
    }
};
/////////////end of instruction super class //////////////////////////

class LDI : public Instruction{

    void execute(){
        //not implemented yet
    }
    virtual Instruction* Clone(){
        return new LDI(*this);
    }
};

然后我创建一个类型为Instruction的指针,并尝试指向LDI类型的新实例.

Instruction* ptr;
ptr = new LDI("test", 22);

我得到以下编译器错误.我有什么想法我做错了吗？

functions.h:71: error: no matching function for call to ‘LDI::LDI(std::string&, int&)’
classes.h:54: note: candidates are: LDI::LDI()
classes.h:54: note:                 LDI::LDI(const LDI&)

Answer 1

代码:new LDI(name, val)具体说"使用name和调用LDI构造函数val".

没有LDI构造函数name / val.事实上,我根本没有看到LDI的构造函数.

如果要使用基类的构造函数,请按以下步骤操作:

public LDI(string _name, int _value) // Public constructor for LDI
    : Instruction(_name, _value)     // Delegate to the base-class constructor
{
    // Do more LDI-specific construction here
}