我最近发表了一个问题,有人指出我会犯错!如何安全地更改状态对象之间的状态?
在main()
我正在做一个状态,然后将整数传递给processState()并基于整数它将改变状态(通过销毁状态并创建一个新状态的新实例),或保持不变州。
我指出的主要问题是函数void state_t::changeState(state_t * new_state)
。我删除了“this”,然后指向已删除的“_state”指针指向新的状态......现在,我指出,这显然是一件坏事。
所以问题是:使用不同状态实现这种状态切换的最佳方式是什么?也许_state
需要是一个全局指针指向当前状态还是一些这样的?
Main.cpp的:
#include <QCoreApplication>
#include <QDebug>
#include "statemachine.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
state_t *myState = new testState1();
myState = myState->processState(1);
myState = myState->processState(2);
myState = myState->processState(3);
myState = myState->processState(1);
return a.exec();
}
基本类型:
#include "state_t.h"
state_t::state_t(QByteArray stateName) :
name(stateName),
_state(this)
{
qDebug() << this->name << ": Creating state";
}
state_t::~state_t()
{
qDebug() << this->name << ": Deleting state";
qDebug() << endl;
}
void state_t::changeState(state_t * new_state)
{
// Check if the state has changed
if (this != new_state)
{
qDebug() << this->name << ": State changed to: " << new_state->name;
delete this;
_state = new_state;
}
else
{
qDebug() << this->name << ": State un-changed";
}
}
void state_t::unknownStateEventHandler(int event)
{
qWarning() << this->name << ": Unknown event " << event;
}
State类(可以有很多这样的):
#include "teststate1.h"
testState1::testState1() :
state_t("state1")
{
}
state_t *testState1::processState(int event)
{
qDebug() << name << ": event" << event;
switch (event)
{
case 2:
{
changeState(new testState2());
//changeState_t(testState2);
break;
}
default:
{
unknownStateEventHandler(event);
break;
}
}
return _state;
}
@ScarletAmaranth:这是“所有的冰雹”。我们都会感激人们大喊大叫的时代结束了。 ;) – thokra
@thokra这是一个不愉快的拼写失败,谢谢你,我刚刚删除了评论:) – ScarletAmaranth
@thokra&Scarlet ... lol :) –