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状态模式：允许对象在内部状态改变时改变它的行为，对象看起来好像修改了它的类。
面向过程方法：针对动作，在处理时switch/if-else各个状态，然后分别处理：
#include <iostream>
class GumballMachine
{
public:
GumballMachine()
{
_count = 100;
_state = NO_QUARTER;
}
/* 执行一个动作时，switch/if-else处理所有的状态 */
void InsertQuarter()
{
switch (_state)
{
case SOLD_OUT:
std::cout<<"You can‘t insert a quarter, the machine has sold out."<<std::endl;
break;
case NO_QUARTER:
std::cout<<"接受投币"<<std::endl;
std::cout<<"You inserted a quarter."<<std::endl;
break;
case HAS_QUARTER:
std::cout<<"You can‘t insert another quarter."<<std::endl;
break;
case SOLD:
std::cout<<"Please wait, we‘re already giving you a gumball"<<std::endl;
break;
default:
break;
}
}
void EjectQuarter() {}
void TurnCrank() {}
void Dispense() {}
private:
enum MACHINE_STATE
{
SOLD_OUT = 0,
NO_QUARTER,
HAS_QUARTER,
SOLD,
} ;
MACHINE_STATE _state;
int _count;
};
int main()
{
std::cout<<"State Patten."<<std::endl;
GumballMachine gumballMachine;
gumballMachine.InsertQuarter();
return 0;
}
面向对象方法：使用状态模式，将各个状态封装为类，每个类支持所有动作。使用时，将动作委托给状态类处理。
.h
/* 状态模式的状态接口 */
class State
{
public:
virtual void InsertQuarter() = 0;
virtual void EjectQuarter() = 0;
virtual void TurnCrank() = 0; // 转动曲柄
virtual void Dispense() = 0; // 分发
};
class GumballMachine
{
public:
GumballMachine();
void InsertQuarter();
void SetState(State *state);
State *GetNoQuarterState();
State *GetHasQuarterState();
private:
State *_noQuarterState;
State *_hasQuarterState;
State *_state;
int _count;
};
.c
#include <iostream>
#include "main.h"
/*各个状态类*/
class NoQuarterState : public State
{
public:
NoQuarterState(GumballMachine *pMachine) : _pGumballMachine(pMachine)
{}
virtual void InsertQuarter()
{
std::cout<<"接受投币"<<std::endl;
std::cout<<"You inserted a quarter."<<std::endl;
// 切换状态
_pGumballMachine->SetState(_pGumballMachine->GetHasQuarterState());
}
virtual void EjectQuarter()
{
std::cout<<"Invalid Action."<<std::endl;
}
virtual void TurnCrank()
{
std::cout<<"Invalid Action."<<std::endl;
}
virtual void Dispense()
{
std::cout<<"Invalid Action."<<std::endl;
}
private:
GumballMachine *_pGumballMachine;
};
class QuarterState : public State
{
public:
QuarterState(GumballMachine *pMachine) : _pGumballMachine(pMachine)
{}
virtual void InsertQuarter()
{
std::cout<<"Invalid Action."<<std::endl;
}
virtual void EjectQuarter()
{
std::cout<<"Quarter Returned."<<std::endl;
// 切换状态
_pGumballMachine->SetState(_pGumballMachine->GetNoQuarterState());
}
virtual void TurnCrank()
{
std::cout<<"Crank Truned."<<std::endl;
// 切换状态 ...
_pGumballMachine->SetState(_pGumballMachine->GetNoQuarterState());
}
virtual void Dispense()
{
std::cout<<"Invalid Action."<<std::endl;
}
private:
GumballMachine *_pGumballMachine;
};
//class SoldState : public State
//class SoldOutState : public State
GumballMachine::GumballMachine()
{
_noQuarterState = new NoQuarterState(this);
_hasQuarterState = new QuarterState(this);
_count = 100;
_state = _noQuarterState;
}
/* 执行一个动作时，委托给状态类处理 */
void GumballMachine::InsertQuarter()
{
_state->InsertQuarter();
}
void GumballMachine::SetState(State *state)
{
_state = state;
}
State *GumballMachine::GetNoQuarterState()
{
return _noQuarterState;
}
State *GumballMachine::GetHasQuarterState()
{
return _hasQuarterState;
}
int main()
{
std::cout<<"State Patten."<<std::endl;
GumballMachine gumballMachine;
gumballMachine.InsertQuarter();
return 0;
}
状态模式 -- 学习HeadFirst设计模式记录
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原文地址：http://www.cnblogs.com/ant-wjf/p/4623252.html
