09-命令者模式-C语言实现

命令者模式是一个高内聚的模式，其定义为： Encapsulate a request as an object,thereby letting you parameterize clients with different requests,queue or log requests,and support undoable operations.（将一个请求封装成一个对象，从而让你使用不同的请求把客户端参数化，对请求排队或者记录请求日志，可以提供命令的撤销和恢复功能。）

UML图：

代码实现：

#include <stdio.h>
#include <stdlib.h>

// 命令接口
typedef struct {
    void (*execute)(void*);
    void (*undo)(void*);
} Command;

// 具体命令类
typedef struct {
    Command command;
    void* receiver;
    void (*action)(void*);
    void (*undoAction)(void*);
} ConcreteCommand;

void ConcreteCommand_execute(void* obj) {
    ConcreteCommand* self = (ConcreteCommand*)obj;
    self->action(self->receiver);
}

void ConcreteCommand_undo(void* obj) {
    ConcreteCommand* self = (ConcreteCommand*)obj;
    self->undoAction(self->receiver);
}

ConcreteCommand createConcreteCommand(void* receiver, void (*action)(void*), void (*undoAction)(void*)) {
    ConcreteCommand command;
    command.command.execute = ConcreteCommand_execute;
    command.command.undo = ConcreteCommand_undo;
    command.receiver = receiver;
    command.action = action;
    command.undoAction = undoAction;
    return command;
}

// 调用者类
typedef struct {
    Command* command;
    void (*setCommand)(void*, Command*);
    void (*executeCommand)(void*);
    void (*undoCommand)(void*);
} Invoker;

void Invoker_setCommand(void* obj, Command* command) {
    Invoker* self = (Invoker*)obj;
    self->command = command;
}

void Invoker_executeCommand(void* obj) {
    Invoker* self = (Invoker*)obj;
    self->command->execute(self->command);
}

void Invoker_undoCommand(void* obj) {
    Invoker* self = (Invoker*)obj;
    self->command->undo(self->command);
}

Invoker createInvoker() {
    Invoker invoker;
    invoker.setCommand = Invoker_setCommand;
    invoker.executeCommand = Invoker_executeCommand;
    invoker.undoCommand = Invoker_undoCommand;
    return invoker;
}

// 接收者类
typedef struct {
    void (*action)(void*);
    void (*undoAction)(void*);
} Receiver;

void Receiver_action(void* obj) {
    printf("Receiver performs action.\n");
}

void Receiver_undoAction(void* obj) {
    printf("Receiver undoes action.\n");
}

Receiver createReceiver() {
    Receiver receiver;
    receiver.action = Receiver_action;
    receiver.undoAction = Receiver_undoAction;
    return receiver;
}

int main() {
    Receiver receiver = createReceiver();
    ConcreteCommand command = createConcreteCommand(&receiver, &receiver.action, &receiver.undoAction);
    Invoker invoker = createInvoker();

    invoker.setCommand(&invoker, &command);
    invoker.executeCommand(&invoker);
    invoker.undoCommand(&invoker);

    return 0;
}

在上面的示例代码中，定义了命令接口Command和具体命令类ConcreteCommand，实现了执行和撤销方法来处理具体的命令。

同时还定义了调用者类Invoker，具有设置命令、执行命令和撤销命令的方法，并通过命令对象来调用相应的方法。

还定义了接收者类Receiver，具有执行操作和撤销操作的方法。

在main函数中，首先创建了一个接收者对象receiver，然后创建了一个具体命令对象command，并将接收者对象和相应的操作方法传入。

接着创建了一个调用者对象invoker，通过调用者对象设置命令对象，并执行和撤销命令。