class CShape{public:CShape(int pre_location) { location=pre_location; }~CShape() {}virtual void display() =0;char randomchar();protected:int location;};class CTriangle: virtual public CShape{public:CTriangle(int pre_height, int pre_location): CShape(pre_location) { height=pre_height; }~CTriangle() {}virtual void display();protected:int height;};class CReserveTriangle: public CTriangle{public:CReserveTriangle(int pre_height, int pre_location): CTriangle(pre_height, pre_location) {}~CReserveTriangle() {}virtual void display();protected:int height;};錯(cuò)誤shape.h(28) : error C2512: 'CShape::CShape' : no appropriate default constructor availablequeue.cppwhy?如果在 CShape 的構(gòu)造函數(shù)里面加上 pre_location=0 默認(rèn)參數(shù)就沒有錯(cuò)誤了，但是我不需要默認(rèn)參數(shù)。如果加上 CShape(){} 的話，或者設(shè)置 pre_location=0 默認(rèn)參數(shù)的話，在程序執(zhí)行過(guò)程中，新建一個(gè) CReserveTriangle 類的對(duì)象，如ptr = new CReserveTriangle(1,2)執(zhí)行過(guò)程中, CReserveTriangle 里面的 location 就會(huì)變成 0。如何設(shè)置成 2 呢（就是原來(lái)參數(shù)里面的數(shù)值），難道這個(gè)參數(shù)是不能連帶的嗎
3 回答
慕萊塢森
TA貢獻(xiàn)1810條經(jīng)驗(yàn) 獲得超4個(gè)贊
之所以要提供沒有參數(shù)的構(gòu)造函數(shù)或給參數(shù)賦予初始值，是因?yàn)槎x或動(dòng)態(tài)分配對(duì)象數(shù)組時(shí)需要調(diào)用一個(gè)沒有參數(shù)的構(gòu)造函數(shù)，由于CShape類內(nèi)部給出了一個(gè)帶參數(shù)的構(gòu)造函數(shù)，因而編譯器不會(huì)自動(dòng)給類生成一個(gè)默認(rèn)構(gòu)造函數(shù)，所以創(chuàng)建對(duì)象數(shù)組時(shí)會(huì)出錯(cuò)。給參數(shù)賦予初值的意思是，如果某個(gè)參數(shù)沒有提供值將會(huì)使用默認(rèn)值，否則使用實(shí)參傳遞過(guò)來(lái)的值。
有只小跳蛙
TA貢獻(xiàn)1824條經(jīng)驗(yàn) 獲得超8個(gè)贊
no appropriate default constructor available
是沒有默認(rèn)的構(gòu)造函數(shù)，不是構(gòu)造參數(shù)
CShape(){}
可以連帶，繼承的屬性不能設(shè)置成保護(hù)
public:
int location;
#include <stdio.h>
#include <iostream>
using namespace std;
class CShape
{
public:
CShape() {}
CShape(int pre_location) { location=pre_location; }
~CShape() {}
virtual void display() =0;
char randomchar();
public:
int location;
};
class CTriangle: public CShape
{
public:
CTriangle(int pre_height, int pre_location): CShape(pre_location) { height=pre_height; }
~CTriangle() {}
virtual void display()=0;
private:
int height;
};
class CReserveTriangle: public CTriangle
{
public:
CReserveTriangle(int pre_height, int pre_location): CTriangle(pre_height, pre_location) {}
~CReserveTriangle() {}
virtual void display();
protected:
int height;
};
void CReserveTriangle::display()
{
}
void main( )
{
CReserveTriangle crt(1,2);
cout<< crt.location<<endl;
}
長(zhǎng)風(fēng)秋雁
TA貢獻(xiàn)1757條經(jīng)驗(yàn) 獲得超7個(gè)贊
class CShape
{
public:
CShape(int pre_location) { location=pre_location; }
CShape(){}/////////////////////////////add this line
~CShape() {}
virtual void display() =0;
char randomchar();
protected:
int location;
};
添加回答
舉報(bào)
0/150
提交
取消