在find

本文介绍了在find_if中使用函子的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我想知道如何使用模板函子作为find_if的参数.我不确定语法.

I was wondering how would I use a template functor as an argument for find_if. I'm not sure about the syntax.

例如，假设一个函子从一个产品的多重映射中删除一个产品.为此，我必须扫描"多图，找到产品(使用同等的仿函数)然后将其删除.

For example, suppose a functor that deletes a product from a multimap of products. To do that, I have to "scan" the multimap, find the product (using my equal functor) and delete it.

这是我的相等"函子:

class isEqual { public: isEqual(T* t) : t_(t) {} bool operator()(const pair<int, T*> pair) const { return (pair.second == t_); } private: T* t_; };

这是被称为擦除产品"的函子，在这里我必须使用等于"产品:

and Here's the functor that's called "erase product" where I have to use my 'is equal' product:

class EraseProduct public: EraseProduct(multimap <int, Produit*>& multimap) : multimap_(multimap) {} ; // constructor that initializes 'multimap_' attribute multimap <int, Product*>& operator()(Product* product) { auto it = find_if(multimap_.begin(), multimap_.end(), USE_EQUAL_FUNCTOR_HERE) if (it != multimap_.end) multimap_.erase(it) return multimap_; } private: multimap<int, Product*>& multimap_;

Product 是一个类.所以我的问题是关于我在哪里写了"USE_EQUAL_FUNCTOR_HERE".我找不到正确的语法.我试过了:

Product is a class. So my question is about where I wrote "USE_EQUAL_FUNCTOR_HERE". I can't figure out the correct syntax. I tried:

IsEqual(), IsEqual(product)

和其他一些东西.

提前致谢！

推荐答案

首先，您必须将isEqual设为类模板.如前所述，不是.

然后，您将使用Product作为模板参数来创建实例，并将其用作find_if的参数.

First you have to make isEqual a class template. As posted, it is not.

Then, you would use Product as the template parameter to create an instance and use it as an argument to find_if.

template <typename T> class isEqual { ... };

和

auto it = find_if(multimap_.begin(), multimap_.end(), isEqual<Product>());