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

本文链接：https://blog.youkuaiyun.com/sunyongsunyong/article/details/12910045

本文介绍了一种使用Boost库中的function和bind功能替代传统switch-case的方法，通过创建函数对象映射来简化代码管理和扩展性，特别适用于处理多种类型的物品使用情况。

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工作中需要根据不同类型来调用不同函数接口时，通常使用switch case来实现

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

不断的添加新的需求会导致case分支很多，

使用boost库解决方案：

typedef boost::function<void(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

_handlers[ItemSpecialAttrId::TimeOfDuration]    = boost::bind(&ItemManager::UseTimeOfDuration, this, boost::lambda::_1, boost::lambda::_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);

    map<int, TypeOnUseItemHandler>::iterator itFind = _handlers.find(specialAttrId);//switch 中的判断分支条件  
    if (itFind == _handlers.end())  
        return;  
	if (itFind->second) 
	{
		TypeOnUseItemHandler = itFind->second(roleId, specialAttrValue);  
		TypeOnUseItemHandler(10.000,10);
	}

这样写通过注册的方式来调用不同的函数接口，方便，灵活，如果有新增的case情况直接填写一个：

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

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