[英]Overloaded typecasts don't work
I've built a little class representing a decimal number, called Complex. 我建立了一个表示十进制数字的小类,称为Complex。 I want to be able to cast it to double, so here's my code 我希望能够将其转换为两倍,所以这是我的代码
Complex.h Complex.h
public:
operator double();
Complext.cpp Complext.cpp
Complex::operator double()
{
return _num;
}
_num is a field of type double of course _num是类型为double的字段
That seems to be okay. 看来还可以。 The problem is in another class where I actually try to cast a complex object into double. 问题出在另一类中,我实际上尝试将一个复杂的对象转换为double。 That's my function: 那是我的功能:
const RegMatrix& RegMatrix::operator *= (double num)
{
Complex factor(num);
for(int i=0; i<_numRow; i++)
{
for(int j=0; j<_numCol; j++)
{
Complex temp = _matrix[i][j];
_matrix[i][j] = (double) (temp * factor); //<---ERROR HERE
}
}
return *this;
}
That results in invalid cast from type 'const Complex' to type 'double'
这导致invalid cast from type 'const Complex' to type 'double'
I have no clue why it happens. 我不知道为什么会这样。 Any ideas? 有任何想法吗? Thanks! 谢谢!
You need to make your operator double
a const
function: 您需要使operator double
const
函数:
operator double() const;
and 和
Complex::operator double() const {
return _num;
}
As the error clearly states, the is no conversion to double for a const Complex. 正如错误明确指出的那样, const Complex无法将其转换为双精度 。 Simply define your conversion operator like this: 只需这样定义您的转换运算符:
operator double() const;
Complex::operator double() const
{
return _num;
}
Note the const modifier at the end. 注意最后的const修饰符。 You should really look for information on const-correctness in C++. 您应该真正寻找有关C ++中const正确性的信息。
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