class myClass
{
public:
int myVal;
myClass(int val) : myVal(val)
{
}
myClass& operator+(myClass& obj)
{
myVal = myVal + obj.myVal;
return *this;
}
myClass& operator+(int inVal)
{
myVal = myVal + inVal;
return *this;
}
myClass& operator=(myClass& obj)
{
myVal = obj.myVal;
return *this;
}
};
int _tmain(int argc, _TCHAR* argv[])
{
myClass obj1(10);
myClass obj2(10);
obj1 = obj1 + obj2;
obj1 = 20 + obj2; // Error : No matching operands for operator "+"
return 0;
}
How can I implement operator '+' on integer and myClass object types as operands? (obj1 = 20 + obj2)
You typically implement the binary arithmetic +=
( compound-assignment ) operator as a member function, and +
as a non-member function which makes use of the former; this allows providing multiple overloads of the latter eg as in your case when the two operands to the custom binary arithmetic operators are not of the same type:
class MyClass
{
public:
int myVal;
MyClass(int val) : myVal(val) {}
MyClass& operator+=(int rhs) {
myVal += rhs;
return *this;
}
};
inline MyClass operator+(MyClass lhs, int rhs) {
lhs += rhs;
return lhs;
}
inline MyClass operator+(int lhs, MyClass rhs) {
rhs += lhs;
return rhs;
// OR:
// return rhs + lhs;
}
int main() {
MyClass obj1(10);
MyClass obj2(10);
obj1 = 20 + obj2;
obj1 = obj1 + 42;
}
For general best-practice advice on operator overloading, refer to the following Q&A:
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