命令模式——C++实现

问题描述：

某系统需要提供一个命令集合（注：可以使用链表，栈等集合对象实现），用于存储一系列命令对象，并通过该命令集合实现多次undo()和redo()操作，可以使用加法运算来模拟实现。

类图：

代码：

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#include<iostream>
#include<vector>
#include<stack>
using namespace std;
//接受者
class Adder {
private:
    int num;
public:
    Adder(){
        this->num=0;
    }
    int add(int value) {
        num += value;
        return num;
    }
};
//抽象命令
class Command {
public:
    virtual int execute(int value) = 0;
    virtual int undo() = 0;
    virtual int redo() = 0;
};
//具体命令
class AddCommand : public Command {
private:
    Adder adder;
    stack <int>unStack;
    stack <int>reStack;
public:
    int undo() {
        int i = 0;
        if (unStack.empty()) {
            i = -1;
        }
        else {
            reStack.push(unStack.top());
            unStack.pop();
            if (!unStack.empty()) {
                i = unStack.top();
            }
        }
        return i;
    }
    int redo() {
        int i = 0;
        if (reStack.empty()) {
            i = -1;
        }
        else {//撤回时只要可以可以撤回，则撤回栈一定有数据
            unStack.push(reStack.top());
            i = reStack.top();
            reStack.pop();
        }
        return i;
    }
    int execute(int value) {
        int v = 0;
        v = adder.add(value);
        cout << v << endl;
        unStack.push(v);
        return v;
    }
};
//调用者
class Invoker{
private:
    AddCommand command;
public:
    void setCommand(AddCommand command2) {
        command = command2;
    };
    void compute(int value) {
        command.execute(value);
    };
    void undo() {
        int i = command.undo();
        if (i == -1) {
            cout << "已撤销到初态" << endl;
        }
        else {
            cout << "执行成功，运算结果是：" << i << endl;
        }
    }
    void redo() {
        int i = command.redo();
        if (i == -1) {
            cout << "已恢复至终态" << endl;
        }
        else {
            cout << "执行成功，运算结果是：" << i << endl;
        }
    }
};
//测试函数
int main() {
    Invoker inv;
    AddCommand command;
    inv.setCommand(command);
    //计算
    cout << "计算过程：" << endl;
    inv.compute(1);
    inv.compute(2);
    inv.compute(3);
    //多次撤回
    cout << "undo操作：" << endl;
    inv.undo();
    inv.undo();
    inv.undo();
    inv.undo();
    //多次恢复
    cout << "redo操作：" << endl;
    inv.redo();
    inv.redo();
    inv.redo();
    inv.redo();
}