通过自定义comperator对STL列表进行排序 [英] Sorting STL list by custom comperator

问题描述

嘿伙计们，我看了一些排序示例，我认为我必须构建一个返回bool的comperator，以保持我的列表按该值排序。


这里有相关的代码：

Hey guys, i looked at some sorting examples, and i thought i jsut had to build a comperator which returns bool, in order to keep my list sorted by that value.

here''s the relevent code:

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推荐答案

这是一个页面列表的排序功能。 sort方法可以使用自定义比较器对列表进行排序，但为什么会这样呢？您按照<对列表进行排序运算符就像默认的排序方法一样。你为什么不定义<您的员工类的操作员？

http ：//www.cplusplus.com/reference/stl/list/sort/

Here is a page on the sort function for a list. The sort method can take a custom comparitor for sorting the list, but why would you? You sort your list by the < operator just like the default sorting method does. Why don''t you just define the < operator for your Employee class?

http://www.cplusplus.com/reference/stl/list/sort/

我知道comperator需要args。


我不明白。比较器对他们有什么影响？无论如何，错误信息非常清楚 - 使用& CityHall :: EmployeeComp''来创建指向成员的指针。 -

将

I know the comperator takes to args.

I don''t get it. What does comparator takes to them? Anyway, the error message is quite clear - "use ''&CityHall::EmployeeComp'' to create a pointer to member." -
will

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你的问题是你试图调用成员函数市政府。但是要调用成员函数，你需要有一个类的实例来调用它，并且没有办法将该实例传递给list :: sort。


有一个解决方案：


删除EmployeeComps对CityHall类型对象的依赖。这很容易使它成为一个静态成员函数，它不需要一个对象，并通过类CityHall :: EmployeeComp将它传递给list :: sort。另一种方法是将方法完全移出CityHall类，然后将其置于全局范围内，这可能不太好。

Your problem is that you have tried to call a member function of CityHall. However to call a member function you need to have an instance of the class to call it on and there is no way to pass that instance into list::sort.

There is a solution:

Remove EmployeeComps dependency on having an object of type CityHall. This is easy make it a static member function which do not require an object to all and pass it to list::sort through the class CityHall::EmployeeComp . An alternative is to move the method out of the CityHall class entirely but then that puts it into global scope which is probably not good.

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