Question

我正在尝试使用一个函数来使用存储在结构中的变量来计算答案。每当我编译代码时，我都会遇到有关struct成员的每次使用的错误。我哪里错了？

干杯！

#include <iostream>

using namespace std;

struct rectangle 
{

    double length, width, area, perimeter; // measurements for rectangle

};

int calculations() 
{

rect.area = rect.width * rect.length;

rect.perimeter = rect.width + rect.width + rect.length + rect.length; 

}

 int main() 
{  

rectangle rect; // rect is a rectnagle structure 

cout << "Please enter the length of your rectangle: " << endl; 
cin >> rect.length;
cout << "Please enter the width of your rectnagle: " << endl; 
cin >> rect.width; 

calculations();

cout << "The area of your rectangle is: " << rect.area << endl; 

cout << "The perimieter of your rectnagle is: " << rect.perimeter << endl; 

cout << rect.length << endl;
cout << rect.width << endl; 
cout << rect.area << endl; 
cout << rect.perimeter << endl;  

}

生成的错误是：

Untitled.cpp:15:5: error: use of undeclared identifier 'rect'
rect.area = rect.width * rect.length;
^
Untitled.cpp:15:17: error: use of undeclared identifier 'rect'
rect.area = rect.width * rect.length;
            ^
Untitled.cpp:15:30: error: use of undeclared identifier 'rect'
rect.area = rect.width * rect.length;
                         ^
Untitled.cpp:17:5: error: use of undeclared identifier 'rect'
rect.perimeter = rect.width + rect.width + rect.length + rect.length; 
^
Untitled.cpp:17:22: error: use of undeclared identifier 'rect'
rect.perimeter = rect.width + rect.width + rect.length + rect.length; 
                 ^
Untitled.cpp:17:35: error: use of undeclared identifier 'rect'
rect.perimeter = rect.width + rect.width + rect.length + rect.length; 
                              ^
Untitled.cpp:17:48: error: use of undeclared identifier 'rect'
rect.perimeter = rect.width + rect.width + rect.length + rect.length; 
                                           ^
Untitled.cpp:17:62: error: use of undeclared identifier 'rect'
rect.perimeter = rect.width + rect.width + rect.length + rect.length; 
                                                         ^
8 errors generated.

Answer 1

添加参数：

void calculations(rectangle& rect) 
{

    rect.area = rect.width * rect.length;

    rect.perimeter = rect.width + rect.width + rect.length + rect.length; 

}

然后致电：

calculations(rect);

Answer 2

您尚未声明rect：

int calculations() 
{

rect.area = rect.width * rect.length;

rect.perimeter = rect.width + rect.width + rect.length + rect.length; 

}

在你的例子中移动：

rectangle rect; // rect is a rectnagle structure

使其全球化：

};

rectangle rect; // rect is a rectnagle structure 
int calculations() 
{

Answer 3

void calculations(rectangle &rect) 
{

       rect.area = rect.width * rect.length;

        rect.perimeter = rect.width + rect.width + rect.length + rect.length; 

}

尝试使用它，因为在计算函数范围内没有定义rect

Answer 4

您的函数的问题在于它使用的名称rect不是全局的，并且是在函数定义之后定义的。所以函数什么都不知道什么是rect。

将功能重新定义为

void calculations( rectangle &rect ) 
{
    rect.area = rect.width * rect.length;

    rect.perimeter = rect.width + rect.width + rect.length + rect.length; 
}

并在main中将其称为

calculations( rect );

无法获取访问struct成员的函数

4 个答案: