切记循环内修改判断条件要谨慎

 bug现象：我更改了场景更新时间，将原来一个场景的更新时间改成了3种不同类型分别不同的更新时间，然后场景里面的怪物就不运动了。    
    原代码：
time_t diff = curTick - lastUpdateTick_;
//std::cout<<" diff:"<<diff<<std::endl;


if (diff > 500)
diff = 500;


lastUpdateTick_ = curTick;
for (ScenarioMap::const_iterator it = scenarioMap_.begin(); it != scenarioMap_.end(); it++)
{
it->second->update(diff);
}
 
修改后代码：
for (ScenarioMap::const_iterator it = scenarioMap_.begin(); it != scenarioMap_.end(); it++)
{
Scenario* scene  = it->second; 
if(scene->isTown())  
{  
time_t diff = curTick - townLastUpdateTick_; 
if(diff > townUpdateDiff)  
{  
scene->update(diff);  
townLastUpdateTick_ = curTick; 
} 
}

if(scene->isField())  
{  
time_t diff = curTick - fieldLastUpdateTick_; 
if(diff > fieldUpdateDiff)  
{  
scene->update(diff);  
fieldLastUpdateTick_ = curTick; 
} 
}
}

原因引起：

如果场景更新成功后，修改了判断条件的一个变量townLastUpdateTick_(或ieldLastUpdateTick_ )，会导致循环后面的本来成功的判断都会失败。 

      谨记这种因为错误的更改了 循环内的判断条件的值 引起的bug。