C++ 如何修复“二进制表达式的无效操作数”错误？
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How to fix a "invalid operands to binary expression" error?
提问by
I am inexperienced of using c++ and stuck at the point where compiler generates invalid operands to binary expression
我没有使用 c++ 的经验，并停留在编译器为二进制表达式生成无效操作数的地方
class Animal{
public:
int weight;
};
int main(){
Animal x, y;
x.weight = 33;
y.weight = 3;
if(x != y) {
// do something
}
}
I want to use x and compare with y, without modifying code i.e. (x.weight != y.weight)in the main code. How should I approach this problem from external class or definition ?
我想使用 x 并与 y 进行比较，而不修改主代码中的代码，即 (x.weight != y.weight)。我应该如何从外部类或定义解决这个问题？
采纳答案by Sambuca
Alternatively you can add the operator overload as non-member:
或者，您可以将运算符重载添加为非成员：
#include <iostream>
using namespace std;
class Animal{
public:
int weight;
};
static bool operator!=(const Animal& a1, const Animal& a2) {
return a1.weight != a2.weight;
}
int main(){
Animal x, y;
x.weight = 33;
y.weight = 3;
if(x != y) {
cout << "Not equal weight" << endl;
}
else {
cout << "Equal weight" << endl;
}
}
回答by TobiMcNamobi
As suggested in the comments you need to overload the !=operator, for example
正如评论中所建议的，您需要重载!=运算符，例如
class Animal{
public:
int weight;
bool operator!=(const Animal &other)
{
return weight != other.weight;
}
};
An expression x != yis like a function call to this operator, in fact it is the same as x.operator!=(y).
表达式x != y就像是对这个运算符的函数调用，实际上它与x.operator!=(y).
