命令模式

Command模式也叫命令模式，是行為設計模式的一種。Command模式通過被稱為Command的類封裝了對目標對象的調用行為以及調用參數。

在面向對象的程序設計中，一個對象調用另外一個對象，一邊情況下調用的過程是，創(chuàng)建目標對象實例；設置調用參數，調用目標對象的方法。

但是有些情況下有必要使用一個專門的類對這種調用過程加以封裝，我們把這種專門的類稱作Command類。

整個調用過程比較繁雜，或者存在多處這種調用。這時，使用Command類對該調用加以封裝，便于功能的再利用。

調用前后需要對調用參數進行某些處理。調用前后需要進行某些額外的處理，比如日志，緩存、記錄歷史操作等。

角色和職責

Command

Command命令的抽象類

ConcreteCommand

ConcreteCommand的具體實現類

Receiver

Invorker

通過Invorker執(zhí)行Command對象

適用于

是將一個請求封裝為一個對象，從而使你可以使用不同的請求，對客戶端進行參數初始化；對請求排隊或記錄請求日志，以及支持可撤銷的操作

僅僅實現命令的執(zhí)行

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首先實現，后半部分，也就是實現命令的執(zhí)行，前面半部分相當于當看病的人多的時候需要，需要排隊，這似乎invoker就開始登場啦。

// // Created by andrew on 2020/11/23. // #include <iostream>using namespace std;class Doctor { public:void treatEye() {cout << "treat eye" << endl;}void treatNose() {cout << "treat nose" << endl;} };class CommandTreatEye { public:explicit CommandTreatEye(Doctor *doctor) {m_doctor = doctor;}void treat() {m_doctor->treatEye();}private:Doctor *m_doctor; };class CommandTreatNose { public:explicit CommandTreatNose(Doctor *doctor) {m_doctor = doctor;}void treat() {m_doctor->treatNose();}private:Doctor *m_doctor; };int main(int argc, char *argv[]) {// 通過一個命令 調用醫(yī)生實現病的治療Doctor *dcotor = new Doctor;CommandTreatEye *commandTreatEye = new CommandTreatEye(dcotor);commandTreatEye->treat();delete commandTreatEye;delete dcotor;return 0; }

完整的實現，支持排隊+執(zhí)行的命令模式

// // Created by andrew on 2020/11/23. // #include <iostream> #include <list>using namespace std;class Doctor { public:void treatEye() {cout << "treat eye" << endl;}void treatNose() {cout << "treat nose" << endl;} };class Command { public:virtual void treat() = 0;virtual ~Command() = default; };class CommandTreatEye : public Command { public:explicit CommandTreatEye(Doctor *doctor) {m_doctor = doctor;}void treat() override {m_doctor->treatEye();}private:Doctor *m_doctor; };class CommandTreatNose : public Command { public:explicit CommandTreatNose(Doctor *doctor) {m_doctor = doctor;}void treat() override {m_doctor->treatNose();}private:Doctor *m_doctor; };//小護士 class BeautyNurse { public:explicit BeautyNurse(Command *command) {this->command = command;}void SubmittedCase() { // 提交病歷 下單命令command->treat();}private:Command *command; };class HeadNurse { public:HeadNurse() {m_list.clear();}void setCommand(Command *command) {m_list.push_back(command);}void SubmittedCase() { // 提交命令for (auto & it : m_list) {it->treat();}}private:list<Command *> m_list; };void nurseCommand() {BeautyNurse *beautyNurse = nullptr;Doctor *doctor = nullptr;Command *command = nullptr;doctor = new Doctor; //command = new CommandTreatNose(doctor);beautyNurse = new BeautyNurse(command);beautyNurse->SubmittedCase();delete doctor;delete command;delete beautyNurse; }void headNurseCommand() { // 護士長 提交病歷 給以上看病HeadNurse *headNurse = NULL;Doctor * doctor = NULL;Command *command1 = NULL;Command *command2 = NULL;doctor = new Doctor;command1 = new CommandTreatEye(doctor);command2 = new CommandTreatNose(doctor);headNurse = new HeadNurse;headNurse->setCommand(command1);headNurse->setCommand(command2);headNurse->SubmittedCase(); // 護士長 批量下單命令delete doctor;delete command1;delete command2;delete headNurse; }int main(int argc, char *argv[]) {// 通過一個命令 調用醫(yī)生實現病的治療 命令的執(zhí)行部分實現/* Doctor *dcotor = new Doctor;CommandTreatEye *commandTreatEye = new CommandTreatEye(dcotor);commandTreatEye->treat();delete commandTreatEye;delete dcotor;*///nurseCommand();headNurseCommand();return 0; }

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