cast operator轉型運算子
Prerequisites:
在建構子轉型的文章中，是把string轉成類別、int轉成類別、double轉成類別
cast operator，把類別轉型成某種類型，比如類別轉成int、類別轉成string、類別轉成float
語法，必須放在類別中，沒有傳回值類型，不能有參數。
operator 類型()
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int main() {
Student student;
student.name_ = "Bill";
student.age_ = 20;
student.weight_ = 50;
// 自動轉型
string name = student;
int age = student;
double weight = student;
cout << "name = " << name << endl;
cout << "age = " << age << endl;
cout << "weight = " << weight << endl;
// 強制轉型
string name2 = (string)student;
int age2 = (int)student;
double weight2 = (double)student;
cout << "name2 = " << name2 << endl;
cout << "age2 = " << age2 << endl;
cout << "weight2 = " << weight2 << endl;
string name3 = string(student);
int age3 = int(student);
double weight3 = double(student);
cout << "name3 = " << name3 << endl;
cout << "age3 = " << age3 << endl;
cout << "weight3 = " << weight3 << endl;
return 0;
}
name = Bill
age = 20
weight = 50
name2 = Bill
age2 = 20
weight2 = 50
name3 = Bill
age3 = 20
weight3 = 50