为什么我会收到错误? [英] Why am I getting errors?
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问题描述
我刚开始使用课程,我在学校忘记了我的c ++参考书,所以请你告诉我为什么我的cin语句中出现错误请:
I'm new to using classes and I forgot my c++ reference book at school so could you please tell me why I am getting errors in my cin statements please :)
#include<iostream>
using namespace std;
class Fraction{
public:
int num1, num2, den1, den2;
int calnum, calden;
};
void add();
void subtract();
void multiply();
void divide();
int main(){
Fraction calculate;
cout << "Enter operations";
cin >> Fraction.num1;
cin >> Fraction.num2;
cin >> Fraction.den1;
cin >> Fraction.den2;
}
推荐答案
两个问题......
1.你使用的是类(类型) )nameFraction
而不是object(实例)namecalculate
...
2。你永远不会初始化计算
所以它将为null,无论如何你都会有一些null-reference-exception ...
As Carlo - 理所当然地说,它是C ++,所以不需要单独初始化...
Two problems...
1. You use the class (type) nameFraction
instead of object (instance) namecalculate
...
2. You never initializecalculate
so it will be null and you will have some null-reference-exception anyway...
As Carlo - rightfully - stated, it is C++, so no need of separate initialization...
如果你错过了参考书,你不需要感到迷茫。如果您有足够的Internet访问权来提出这个问题,那么您可以直接获得C ++引用和C ++库引用,特别是:
https://msdn.microsoft.com/en-us/library/3bstk3k5.aspx [ ^ ](但请记住,它还包括您可能或许多人不需要的C ++ / CLI, http://en.wikipedia.org/wiki/C%2B%2B/CLI [<一个href =http://en.wikipedia.org/wiki/C%2B%2B/CLItarget =_ blanktitle =New Window> ^ ]),
http://www.cplusplus.com/reference [ ^ ],
http://www.tutorialspoint.com/cplusplus/cpp_references.htm [ ^ ],
http://www.learncpp.com [ ^ ],
http://www.cplusplus.com [ ^ ]。
此外,它可能是比询问这些问题更快,同时更有用,因为当你找到自己需要的东西时,你会学到更多的技能。
-SA
If you are missing your reference book, you don't need to feel lost. If you have enough of Internet access to ask this question, you have everything to get directly to C++ references and C++ libraries references, in particular:
https://msdn.microsoft.com/en-us/library/3bstk3k5.aspx[^] (but remember, it also covers C++/CLI which you may or many not need, http://en.wikipedia.org/wiki/C%2B%2B/CLI[^]),
http://www.cplusplus.com/reference[^],
http://www.tutorialspoint.com/cplusplus/cpp_references.htm[^],
http://www.learncpp.com[^],
http://www.cplusplus.com[^].
Also, it could be faster than asking such questions and more useful at the same time, because, when you find what you need by yourself, you learn more skills.
—SA
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