我有一个被类继承的银行基类“储蓄”,“支票”,“流动”和“投资”。 我正在为我的学校练习多态性。
我有一个代码,这是相当长的,我不能在这里分享。 我在这段代码中所做的就是在指针this->bank处分配动态数组(我有单独的函数,grow2D),并通过询问用户是否想要创建“储蓄”,“检查”,“当前”或“投资”帐户的对象来在运行时上创建对象。 我的问题是,在通过询问用户创建对象之后,如何检查特定索引中的对象类型(“保存”,“检查”,“当前”或“投资”)。
例如,使用在Bank[0]创建了一个类型为“Savings”的对象。 当user添加完所有帐户后,我怎样才能在代码中找到Bank[0]上的对象类型呢?
string name;
unsigned long long int accountNumber;
unsigned long int balance;
int option = 0;
size++;
this->bank = grow2D(bank, size);
cout <<endl << "1 for Saving" << endl;
cout << "2 for Checking" << endl;
cout << "3 for Current" << endl;
cout << "4 for Investment" << endl;
cout << "Enter option";
cin >> option;
cin.ignore();
cout << "Enter name";
getline(cin, name);
cout << "Enter Account Number";
cin >> accountNumber;
cout << "Enter Balance";
cin >> balance;
if(option==1)
{
int interestRate;
cout << "Enter Interest Rate: ";
cin >> interestRate;
bank[size - 1] = new Saving(name,accountNumber,balance,interestRate);
}
else if (option == 2)
{
int fee;
cout << "Enter Fee: ";
cin >> fee;
bank[size - 1] = new Checking(name, accountNumber, balance,fee);
}
else if (option == 3)
{
int fee;
unsigned long int minimumBalance;
cout << "Enter Fee: ";
cin >> fee;
cout << "Enter Minimum balance: ";
cin >> minimumBalance;
bank[size - 1] = new Current(name, accountNumber, balance,fee,minimumBalance);
}
else if (option == 4)
{
int fee;
unsigned long int minimumBalance;
int profit;
cout << "Enter Fee: ";
cin >> fee;
cout << "Enter Minimum balance: ";
cin >> minimumBalance;
cout << "Enter Profit: ";
cin >> profit;
bank[size - 1] = new Investment(name, accountNumber, balance, fee, minimumBalance,profit);
}
假设您的类至少包含一个虚拟方法(至少析构函数应该是虚拟的),例如:
class Saving {
public:
virtual ~Saving() = default;
};
class Checking: public Saving {};
class Current: public Saving {};
class Investment: public Saving {};
然后可以使用TypeID()
查询对象的运行时类型。
示例:
#include <typeinfo>
Saving* s = new Current();
if(typeid(*s) == typeid(Current)) {
std::cout << "It's a Current!" << std::endl;
}
if(typeid(*s) == typeid(Investment)) {
std::cout << "It's an Investment!" << std::endl;
}
或者,您还可以使用dynamic_cast()
并检查是否成功转换为派生类型:
Saving* s = new Investment();
Investment* investment = dynamic_cast<Investment*>(s);
if(investment != nullptr) {
std::cout << "It's an Investment!" << std::endl;
}
Current* current = dynamic_cast<Current*>(s);
if(current != nullptr) {
std::cout << "It's a Current!" << std::endl;
}
// etc...