State形式

意图：允许一个对象在其内部状态改变时改变它的行为；对象看起来似乎修改了它的类；在一个状态即将结束的时候启用下一个状态，可以是一个按需的连锁反应；

适用性：

1、一个对象的行为取决于它的状态，并且它必须在运行过程中可以根据它的状态改变它的行为；

2、一个操作中含有庞大的多分支的条件语句，并且这些分支依赖于该对象的状态；这个状态通常使用一个或多个枚举常量表示；通常，有多个操作包含这一相同的条件结构；State模式把每一个条件分支放入一个独立的类中；这使得你可以根据对象自身的情况把对象的状态作为一个对象，而且这一对象可以不依赖于其它对象而独立变化；

结构图：

应用： #ifndef _STATE_H_ #define _STATE_H_ #include <iostream> #include <string> using namespace std; class TCPStream; //需要被改变状态的对象类;它聚合了一个状态对象:TCPState;依据TCPState对象的变化来改变TCPConnection对象的行为; class TCPConnection { public: TCPConnection(void); ~TCPConnection(void); void ActiveOpen(void); void PassiveOpen(void); void Close(void); void Send(void); void Acknowledge(void); void Synchronize(void); void ProcessStream(TCPStream*); private: friend class TCPState; void ChangeState(TCPState*); private: TCPState* m_lpState; }; //TCPConnection类对象的状态对象:TCPState;它实现为一个纯虚基类; class TCPState { public: TCPState(void); virtual ~TCPState(void); virtual void Transmit(TCPConnection*, TCPStream*); virtual void ActiveOpen(TCPConnection*); virtual void PassiveOpen(TCPConnection*); virtual void Close(TCPConnection*); virtual void Synchronize(TCPConnection*); virtual void Acknowledge(TCPConnection*); virtual void Send(TCPConnection*); protected: void ChangeState(TCPConnection*, TCPState*); }; //连接已建立状态 class TCPEstablished: public TCPState { public: virtual ~TCPEstablished(void); static TCPState* Instance(void); virtual void Transmit(TCPConnection*, TCPStream*); virtual void Close(TCPConnection*); private: TCPEstablished(void); }; //连接关闭状态 class TCPClosed: public TCPState { public: virtual ~TCPClosed(void); static TCPState* Instance(void); virtual void ActiveOpen(TCPConnection*); virtual void PassiveOpen(TCPConnection*); private: TCPClosed(void); }; //监听状态类 class TCPListen: public TCPState { public: ~TCPListen(void); static TCPState* Instance(void); virtual void Send(TCPConnection*); private: TCPListen(void); }; TCPConnection::TCPConnection(void) { this->m_lpState = TCPClosed::Instance(); cout << "call TCPConnection()" << endl; } TCPConnection::~TCPConnection(void) { cout << "call ~ TCPConnection()" << endl; } void TCPConnection::ActiveOpen(void) { this->m_lpState->ActiveOpen(this); cout << "TCPConnection active-open state" << endl; } void TCPConnection::PassiveOpen(void) { this->m_lpState->PassiveOpen(this); cout << "TCPConnection passive-open state" << endl; } void TCPConnection::Close(void) { this->m_lpState->Close(this); cout << "TCPConnection close state" << endl; } void TCPConnection::Send(void) { this->m_lpState->Send(this); cout << "TCPConnection send state" << endl; } void TCPConnection::Acknowledge(void) { this->m_lpState->Acknowledge(this); cout << "TCPConnection ack state" << endl; } void TCPConnection::Synchronize(void) { this->m_lpState->Synchronize(this); cout << "TCPConnection sync state" << endl; } void TCPConnection::ProcessStream(TCPStream* st) { cout << "TCPConnection ProcessStream" << endl; } void TCPConnection::ChangeState(TCPState* state) { if(this->m_lpState) { delete this->m_lpState; this->m_lpState = NULL; } this->m_lpState = state; cout << "TCPConnection::ChangeState()" << endl; } TCPState::TCPState(void) { cout << "call TCPState()" << endl; } TCPState::~TCPState(void) { cout << "call ~ TCPState()" << endl; } void TCPState::Transmit(TCPConnection*, TCPStream*) { cout << "TCPState::Transmit()" << endl; } void TCPState::ActiveOpen(TCPConnection*) { cout << "TCPState::ActiveOpen()" << endl; } void TCPState::PassiveOpen(TCPConnection*) { cout << "TCPState::PassiveOpen()" << endl; } void TCPState::Close(TCPConnection*) { cout << "TCPState::Close()" << endl; } void TCPState::Synchronize(TCPConnection*) { cout << "TCPState::Synchronize()" << endl; } void TCPState::Acknowledge(TCPConnection*) { cout << "TCPState::Acknowledge()" << endl; } void TCPState::Send(TCPConnection*) { cout << "TCPState::Send()" << endl; } void TCPState::ChangeState(TCPConnection* conn, TCPState* state) { cout << "TCPState::ChangeState()" << endl; conn->ChangeState(state); } //监听状态类 TCPListen::~TCPListen(void) { cout << "call ~ TCPListen()" << endl; } TCPState* TCPListen::Instance(void) { return new TCPListen(); } void TCPListen::Send(TCPConnection* conn) { //send SYN, recv SYN ACK, etc; this->ChangeState(conn, TCPEstablished::Instance()); } TCPListen::TCPListen(void) { cout << "call TCPListen()" << endl; } TCPClosed::~TCPClosed(void) { cout << "call ~ TCPClosed()" << endl; } TCPState* TCPClosed::Instance(void) { return new TCPClosed(); } TCPClosed::TCPClosed(void) { cout << "call TCPClosed()" << endl; } void TCPClosed::ActiveOpen(TCPConnection* conn) { //send SYN, receive SYN,ACK; etc. this->ChangeState(conn, TCPEstablished::Instance()); } void TCPClosed::PassiveOpen(TCPConnection* conn) { // send FIN, receive ACK of FIN, etc; this->ChangeState(conn, TCPListen::Instance()); } TCPEstablished::~TCPEstablished(void) { cout << "call ~ TCPEstablished()" << endl; } TCPState* TCPEstablished::Instance(void) { return new TCPEstablished(); } void TCPEstablished::Transmit(TCPConnection* conn, TCPStream* st) { conn->ProcessStream(st); } void TCPEstablished::Close(TCPConnection* conn) { this->ChangeState(conn, TCPListen::Instance()); } TCPEstablished::TCPEstablished(void) { cout << "call TCPEstablished()" << endl; } class StateApplication { public: StateApplication(void); ~StateApplication(void); int doRun(void); }; StateApplication::StateApplication(void){} StateApplication::~StateApplication(void){} int StateApplication::doRun(void) { TCPConnection tcpConn; tcpConn.ActiveOpen(); tcpConn.Acknowledge(); tcpConn.Send(); tcpConn.Synchronize(); tcpConn.Close(); tcpConn.PassiveOpen(); tcpConn.Close(); return 0; } #endif #include "State.h" int main(int argc, char** argv) { StateApplication oApp; oApp.doRun(); return 0; }