软件设计22|状态模式（C++）

用C++模拟实现课堂上的“银行账户”的实例，要求编写客户端测试代码模拟用户存款和取款，注意账户对象状态和行为的变化。

“银行账户”实例:

一、效果如下：

二、类图如下：

三、代码如下：

#include<iostream>
using namespace std;

class Account;

class AccountState {
public:
    virtual void stateCheck(Account* account) = 0;
};

class Account
{
private:
    AccountState* state;//当前状态
    int balance;// 余额
    int amount;// 取款金额
    int cash;//存款金额
public:
    Account() {}
    //ATM状态
    void setState(AccountState* state) {
        this->state = state;
    }
    //取款操作
    void withdraw(int amount) {
        if (balance < -1000) {
            cout << "您已处于透支状态，请先存款！！！" << endl;
            cout << "账户余额：" << balance << endl;
        }
        else {
            cout << "向账户提出申请：取款:" << amount << "元。" << endl;
            if (amount != 0) {
                balance = balance - amount;
                cout << "取款成功，余额为：" << balance << endl;
            }
        }
    }
    //存款操作
    void deposit(int cash) {
        cout << "向账户提出申请：存款:" << cash << "元。" << endl;
        if (cash != 0) {
            balance = balance + cash;
            cout << "存款成功，余额为：" << balance << endl;
        }
    }
    //状态
    void stateCheck() {
        state->stateCheck(this);
    }
    //余额
    int getBalance() {
        return balance;
    }
    void setBalance(int balance) {
        this->balance = balance;
        cout << "账户余额为：" << balance << endl;
    }
    //取款金额
    int getAmount() {
        return amount;
    }
    //存款金额
    int getCash() {
        return cash;
    }
};

//账户的状态为黄色(YellowState)，即欠费状态，此时既可以向该账户存款也可以从该账户取款
class YellowState : public AccountState {
private:
    Account* account;
public:
    void stateCheck(Account* account) {
        cout << "欠费状态，此时既可以向该账户存款也可以从该账户取款" << endl;
    }
};

//账户的状态为绿色(GreenState)，即正常状态，表示既可以向该账户存款(deposit)也可以从该账户取款(withdraw)
class GreenState :public AccountState {
private:
    Account* account;
public:
    void stateCheck(Account* account) {
        cout << "正常状态，表示既可以向该账户存款(deposit)也可以从该账户取款(withdraw)" << endl;
    }
};

//账户的状态为红色(RedState)，即透支状态，此时用户只能向该账户存款，不能再从中取款
class RedState :public AccountState {
private:
    Account* account;
public:
    void stateCheck(Account* account) {
        cout << "透支状态，此时用户只能向该账户存款，不能再从中取款" << endl;
    }
};

int main() {
    Account* account = new Account();
    Account* account1 = new Account();
    Account* account2 = new Account();

    cout << "******************************" << endl;
    cout << "***********Account1***********" << endl;
    account->setBalance(1000);
    account->setState(new GreenState());
    account->stateCheck();
    account->deposit(200);
    account->withdraw(300);
    account->getBalance();
    cout << endl;

    cout << "******************************" << endl;
    cout << "***********Account2***********" << endl;
    account1->setBalance(-2000);
    account1->setState(new RedState());
    account1->stateCheck();
    account1->deposit(200);
    account1->withdraw(300);
    account1->getBalance();
    cout << endl;

    cout << "******************************" << endl;
    cout << "***********Account3***********" << endl;
    account2->setBalance(-200);
    account2->setState(new YellowState());
    account2->stateCheck();
    account2->deposit(200);
    account2->withdraw(300);
    account2->getBalance();
}