[error] request for member 'area' in 'r' which is non-class type 'float' 是什么意思？答案

【问题标题】：Waht does [error] request for memebr 'area' in 'r' which is of non-class type 'float' mean?[error] request for member 'area' in 'r' which is non-class type 'float' 是什么意思？
【发布时间】：2016-12-07 15:42:04
【问题描述】：

我是编码新手，我正在尝试编写一个具有多态性但我的矩形部分不起作用的程序。我试图在所有三个文件中添加变量以适应它，但我不断收到错误。下面的代码是我解决此问题的最新尝试。我现在得到的错误是“r”中的成员“区域”的[错误]请求，这是非类类型“float”和“r”中的参数，这是非类类型“float”。在这一点上，我不知道如何解决这个问题。可以的话请帮忙！

Main.cpp

#include <iostream>
#include "shape.h"
#include "shape.cpp"

using namespace std;
int main() {
    float r, a, b, a1, b1;
    cout<<"This program will ask you to input some data in order to find the area and the parameter of 3 shapes."<<endl;
    cout<<"\nInput the circles radius --everything should be in inches (i.e 5):";
    cin>>r;
    Circle c(r);
    cout<<"\nPlease input two side of the Right Triangle excluding the hypotenuse-- everything should be in inches( i.e 5 5): ";
    cin>>a>>b;
    RTriangle rt(a,b);  
    cout<<"\nPlease input two side of the Rectangle -- everything should be in inches( i.e 5 5): ";
    cin>>a>>b;
    Rectangle r(a1,b1);
    cout<<"\n\nThe Circles Area is:"<<c.area()<<" inches, The Parameter  is:"<<c.parameter()<<" inches"<<endl;
    cout<<"The Rectangle Area is:"<<r.area()<<" inches, The Parameter is:"<<r.parameter()<<endl;
    cout<<"The Right Triangle Area is:"<<rt.area()<<" inches, The Parameter is:"<<rt.parameter()<<" inches"<<endl;
    cout<<"Thanks once agin for using this program for your AREA and PARAMETER needs!"<<endl;
    system ("PAUSE");
    return 0;
}

形状.cpp

#include"shape.h"

Shape::Shape(){
    sideA = sideB = 0;
}

Shape::Shape(int a, int b){
    sideA = a;
    sideB = b;  
}

//these will get overrided
float Shape::area(){return 0;}
float Shape::parameter(){return 0;}
//rectangle definations
Rectangle::Rectangle(float a, float b):Shape(a,b){
//calling parent class constructor
}

float Rectangle::area(){
    return sideA*sideB; 
}

float Rectangle::parameter(){
    return 2*(sideA+sideB);
}

//right triangle definations
RTriangle::RTriangle(float h, float w):Shape(h, w){
}

float RTriangle::area(){
    return 0.5*sideA*sideB;
}
float RTriangle::parameter(){
    float hyp = sqrt(sideA*sideA + sideB*sideB);
    return sideA + sideB + hyp;
}

//circle definations
Circle::Circle(float r){
    sideA = r;
}

float Circle::area(){
    return 3.14 * sideA * sideA;
}

float Circle::parameter(){
    return 2 * 3.14 * sideA;
}

形状.h

#ifndef SHAPES
#define SHAPES
#include<cmath>

class Shape {
protected:
    float sideA, sideB;
    float radius;
public:
    Shape();
    Shape(int,int);
    virtual float area();
    virtual float parameter();
};

class Rectangle : public Shape{
public:
    Rectangle(float a, float b);
    float area();
    float parameter();
};

class RTriangle : public Shape{
public:
    RTriangle(float h, float w);
    float area();
    float parameter();
};

class Circle : public Shape{
public:
    Circle(float r);
    float area();
    float parameter();
};

#endif

【问题讨论】：

标签： c++ constructor compiler-errors polymorphism

【解决方案1】：

看看Main.cpp，你会发现两行类似

float r, a, b, a1, b1;

和

Rectangle r(a1,b1);

如您所见，r 被定义了两次。我建议用Rectange rect(a1, b1); 替换Rectangle r(a1,b1); 这应该会有所帮助。

【讨论】：