boost::function 用来注册函数(switch N多case的解决方案)

在现在做的游戏开发的项目中，需要根据道具类型调用不同的接口，通常的写法是用

switch(itemType)
{
 case ...;
 case ...;
.
.
.
}

这样写的话，如果将来有新增情况会导致case越来越多 ，不好。

正好项目中使用了boost库，结果想了个解决方案：

	typedef boost::function<void(long long, int)> TypeOnUseItemHandler; // 回调函数返回void 参数一个是long long型，一个是int型
	map<int, TypeOnUseItemHandler> _handlers; // 定义map<key, value>  key是case的条件  value是执行的接口

// 注册
	_handlers[ItemSpecialAttrId::TimeOfDuration]	= boost::bind(&ItemManager::UseTimeOfDuration, this, _1, _2);
	_handlers[ItemSpecialAttrId::StorgeHpVolume]	= boost::bind(&ItemManager::UseStorgeHpVolume, this, _1, _2);
	_handlers[ItemSpecialAttrId::IsGetItem]			= boost::bind(&ItemManager::UseIsGetItem, this, _1, _2);
	_handlers[ItemSpecialAttrId::ItemBuff]			= boost::bind(&ItemManager::UseItemBuff, this, _1, _2);
	_handlers[ItemSpecialAttrId::Bind]				= boost::bind(&ItemManager::UseBind, this, _1, _2);
	_handlers[ItemSpecialAttrId::ReinforceLevel]	= boost::bind(&ItemManager::UseReinforceLevel, this, _1, _2);
	_handlers[ItemSpecialAttrId::AddPartnerExp]		= boost::bind(&ItemManager::UseAddPartnerExp, this, _1, _2);
	_handlers[ItemSpecialAttrId::AddRoleExp]		= boost::bind(&ItemManager::UseAddRoleExp, this, _1, _2);
	_handlers[ItemSpecialAttrId::AddSliver]			= boost::bind(&ItemManager::UseAddSliver, this, _1, _2);
	_handlers[ItemSpecialAttrId::AddGold]			= boost::bind(&ItemManager::UseAddGold, this, _1, _2);
	_handlers[ItemSpecialAttrId::AddGoldNote]		= boost::bind(&ItemManager::UseAddGoldNote, this, _1, _2);
	_handlers[ItemSpecialAttrId::SynthMaterial]		= boost::bind(&ItemManager::UseSynthMaterial, this, _1, _2);
	_handlers[ItemSpecialAttrId::EnhanceNpcExp]		= boost::bind(&ItemManager::UseEnhanceNpcExp, this, _1, _2);
	_handlers[ItemSpecialAttrId::GetAttribute]		= boost::bind(&ItemManager::UseGetAttribute, this, _1, _2);
	_handlers[ItemSpecialAttrId::GainReinforceProp] = boost::bind(&ItemManager::UseGainReinforceProp, this, _1, _2);

//specialAttrId 是外部传递过来的参数 对应map中的key
	map<int, TypeOnUseItemHandler>::iterator itFind = _handlers.find(specialAttrId);
	if (itFind == _handlers.end())
		return;
	if (itFind->second)
		itFind->second(roleId, specialAttrValue);

这样写 通过注册的方式来调用不同的函数接口，看着舒服多了，也灵活多了， 到有新增的case情况 直接填写一个：

	_handlers[ItemSpecialAttrId::GainReinforceProp] = boost::bind(&ItemManager::UseGainReinforceProp, this, _1, _2);